I would like to know how to meditate. I'm in a wheelchair, so I can't do yoga. I need to concentrate on breathing. Thanks in advance.

Here are a couple of websites that will hopefully help you :

How to Meditate - Everything you need to Learn Meditation! How to Meditate, Master your mind, and Manifest an Amazing Life that you Love!
https://www.amsa.org/healingthehealer/meditate.cfm
Meditation - Learning How To Meditate - Pioneer Thinking

Good luck! :)