I used to fletch my arrows,and now that I have a crossbow how do you fletch a bolt?

They are arrows so the exact same principles apply.

I understand that but how can I make it fit into my fletcher?

You aren't giving much info to help you with. Are you having problems with a fletching tool? What is it that you find you cannot do? Are you having flight/clearance/fletching position issues? What fletching tool? Is it that the shaft won't go into the tool? Shaft going into the tool too deep?

Get an arizona ezfletch. Make sure you get one that fits your arrow diameter. Its ez.

Good luck, Stan

I found out I just needed a fletching knoc.That was all. When in doubt go to your local archery shop.LOL