So now you have the equipment, you have the route mapped out and so now you have to ride it.
As with anything new like this you should do a recce first, ride the route on a day off and find all the quirks and difficult points it will also give you a real understanding of how long it will take you, the gradients in Sheffield may slow you down. If you do this on a weekend be aware that the traffic will be heavier at rush hour in the week.
There will be lots of people giving you advice and this can be helpful or not depending on your view there are a few things that by and large should be taken on board to ride successfully on the road:
1. See and be seen - To ride a bike confidently you need to know where the traffic is, looking over your shoulder not only allows you to see what is behind you it also indicates to drivers that you may be about to do a manouvre and therefore it is a good habit to get into.
Signalling with your arms about the direction you intend to travel is also critical. Be clear and bold and always follow the signal with a manouvre. At night it is vital that you have lights, flashing lights are good to be seen but if you need to see the road on unlit sections you will need something powerful and continuous. We recently did a review of lights here: http://www.russellsbicycleshed.co.uk/news/2014/11/25/lighting-up
Here's a video you might find interesting. It's from America so they riding on the wrong side of the road :-)
2. Position - Your position on the road also shows your intent and will indicate to drivers if you are confident, this does make a difference to how many will treat you. The Primary Position for a cyclist is in the middle of the lane but generally 1m from the kerb is the best place to be. You should use the Primary Position as frequently as you can to protect yourself and also to avoid punctures and muck along the kerbline. Riding in the gutter is not good practice and puts you at further risk, imagine if a pedestrian step off the kerb in front of you.
Where you encounter pedestrian islands in the road you should gently drift to the middle of the lane to protect yourself from drivers trying to pass too close. This is called 'Taking the Lane', you'll hear it a lot amongst experienced riders. Never ride upto the back of a parked vehicle, anticipate that someone may want to get out of the car and a door may open so you should drift out as far as is safe to avoid this.
Remember this is your road as much as anyone elses and therefore if you are riding slowly up hill in a safe way the drivers will have to wait patiently behind you.
3. Acknowledge good driving - We all hate bad and unsafe driving so why not acknowledge those people who give way to you and wait behind you until its safe to pass. A smile and wave can create a better atmosphere between driver and cyclist.
4. Cycle Lanes - As a new rider you'll want to use these where you can but be warned many lanes in Sheffield are not well maintained and you need to watch out for broken glass and other obstacles like fallen branches. Cycle lanes do allow you to travel in the opposite direction to traffic on many one way streets so its not always the case that the cycle lane is for cyclists travelling in the same direction as the traffic. A good example of this is the Pinstone Street cycle lane in front of the Peace Gardens.
5. Turning right - this is daunting the first time you do it but follow these small steps and you master it in no time. Giving yourself plenty of time and distance (more than you need when driving) look over your shoulder to assess the traffic flow. Extend you right arm fully and begin to drift into the middle of the lane. Apply the brakes and begin to slow gently. Come to the white line at the junction and stop if required. When it is safe to cross the opposite lane turn right. Remember it may take you a few seconds to get going if you have stopped so don't take chances.
What you wear to cycle in is up to you, if you wear trousers get some bicycle clips or tuck them into your socks to avoid oil stains from your bicycle chain. If you wear a skirt watch out for it catching into the wheel as it flapps around. Gloves are great all year round keeping your fingers warm in winter and padding your palms against the handlebars.
First and foremost you need to enjoy it and so do things along your route to enjoy the ride don't be put off by a puncture or even a fall, even World Tour riders fall off.