Practice lap, with tyre pressures somewhere close to where you want them. If you do change them, have another practice lap to check that you have improved the bike. I tend to do my warm ups these days on a turbo trainer, with head phones, 20 minute steady spinning, with good lively music on. Get on the line, and wait for the whistle, as at that point the bull$hit stops. Most of all enjoy it, and think if you aren’t it possibly isn’t for me, but don’t worry as at least you have tried it.