Both approaches work, and understanding the difference helps you choose the one that makes the most financial sense for your situation.
The first option is setting up an AdvancePay account through Securus directly. You fund that account and your boyfriend's calls to your number draw from it. The catch is that Securus charges a transaction fee every time you deposit money, which can be significant depending on the deposit amount and method. Those fees add up over time and represent money going to Securus that does not actually go toward call time.
The second option is for your boyfriend to purchase phone time through the commissary or phone system at Will County. That money goes directly into his account and covers calls without the deposit fees that hit your end when funding an AdvancePay account. Depending on how the facility structures it, this can be a cleaner way to fund calls without the layered fees.
Either way, the most important thing regardless of which funding method you use is having an InmateAid number in place. The funding method determines how the money gets into the system. The InmateAid number determines what rate Securus charges for each call. Those are two separate variables, and getting both right is what maximizes how far your money goes.
Securus is not going to volunteer information about how to reduce your per-call cost. That is not in their interest. InmateAid exists specifically to provide that information and do the work of finding the lowest rate available for Will County. Email aid@inmateaid.com with your current number and the facility name and get an honest estimate before your next deposit.