Even the most experienced Dom or sub faces difficulties when starting a D/s relationship with someone new. Your knowledge of what worked with your previous partner(s) might afford you some insight into possible activities to try, but, of course, it's hard to know exactly what will and won't work with a new partner. You'll have to figure that out together.
Sometimes, too much experience can even be a negative thing. Factors such as learned behaviour, expectations and assumptions from past relationships can often be carried forward into new relationships, and this rarely works out well.
The key to a good D/s relationship is, without doubt, communication and connection, not experience. If you have found a partner whom you feel you can be open and honest with and are connected to, then you are most definitely on the right path. Experience will grow between the two of you as you explore and learn together, and that's the fun part!
Don't be afraid to make mistakes. Know-it-alls are dangerous in my opinion, and we all misstep sometimes. That doesn't mean that you should be reckless (especially not about protection), but mistakes will happen. Prepare for them as best you can and always try to learn from them.
This is a question that is close to my heart, because when I met my husband, we were both novices. Like you I had played online, and also had had one short relationship which featured D/s play scenes, but that was it. I knew I was a sub but I didn't really know what that specifically meant for me. My husband had always enjoyed being a Top in the bedroom but had never been a Dom before and had only indulged in fairly light D/s play.