The number your inmate dials is the one InmateAid assigns to your account. It arrives in an email notification sent to your inbox about an hour after your purchase is complete. Check that email, find the assigned number, and get it to your inmate so they can add it to their approved call list at the facility.
That assigned number is a forwarding number. When your inmate dials it from the facility's phone system, the call routes directly to whatever number you designated as your forward-to number during setup. From your inmate's end it works like any other call. From your end it rings through to your cell phone or landline as normal.
Before anything else, double-check that the forward-to number in your account is correct. If that number is wrong, calls will not reach you even if your inmate is dialing correctly. Log into your InmateAid account and confirm the forwarding destination is exactly right. That is the most common setup issue and it is easy to fix before it becomes a problem.
Once your inmate has the new number and it is on their approved list, the discounted rate kicks in automatically from that point forward.