First race question

In every race I've done with bike numbers, they have been stickers. No need for any extra equipment to attach them (taking off is sometimes a different story!).

Usually you will receive stickers for your bike. Wearing your bib on a race belt during the bike portion only creates drag and is quite annoying blowing in the wind. Unless the race director requires it, you should not need it during the bike.

You should get 2 stickers: 1 for your bike and 1 for your helmet.

What everybody else says.

My recommendation....
Read the rules. If they don't have rules on their website...you can always ask someone at packet pickup. If they have a race meeting, go to it....and ask any questions. But, the rules will specify what you're supposed to do. It's rare that you'd wear your bib on the bike, but I've done some small races where they required it by the rules....and most seemed to disregard it.

But, I always recommend reading the rules. Especially for a first timer. It was probably (outside of learning to swim, ride and run) the singlemost thing I did that prepared me for the day. For one, it kept me from doing something dumb and looking like a fool. That's A number 1. Number 2 would have been if some sort of 'dangerous' situation had come up....like trying to pass someone on the bike who didn't read the rules...I was arguably quite a bit safer.

Just a really binary way to improve your day. You don't have to be able to run, swim, or ride better to make your day better...simply by reading the rules.
And, also....that doesn't mean freak out about them. Nobody will be out there measuring the distance between you and the next guy on the bike. Unless, of course, you're out front . Best example I can give is it's like the driver's test. You don't need to know exactly how long the cable can be when towing a car. They hardly ever ask that question, but if they do....if you read through the booklet....you'd get the answer right.

If you're following the spirit of the rules, no harm will come.