Ride your ride - that means, although we're cycling in a group session, no rider can see (or judge) how hard you're pedalling. If you want to take the pace a little slower, that's fine - and you're in control of how much resistance you add. If you're not comfortable pedalling out of the saddle, don't worry - stay in the seat, and keep pedalling; you'll still get results - and you'll be working the muscles in your bum and back of your thighs more; win win!
As you get fitter, you'll be able to push harder - that's what's great about indoor cycling; it will always challenge you in a healthy, safe way. Come and enjoy your sessions, without putting pressure on yourself. Enjoy - it's all good.