What make(s) and models(s) are your modem, router, (or modem/router)?
Do you have the User Guides/Manuals? Do you have admin rights to the router or modem/router?
Too many variables to provide a detailed explanation.
However, here is a good link with the basics via Linksys:
https://www.linksys.com/us/support-article?articleNum=136548
Find the same information and instructions with regards to your network and network devices.
Get one Access Point working first, then use what you have learned to set up the second Access Point.
Then post more specific questions if necessary or if a problem occurs.