You can pay your Bank of America Cash Rewards Secured card with a checking account:
By calling 1-800-236-6497
Online
Through BofA's Mobile Banking app for iOS and Android.
You could also use a check or your debit card associated with a checking account to withdraw money from an ATM and pay at a Bank of America financial center or ATM.
Ultimately, you can send a check via mail to the following address:
PO Box 15019
Wilmington, DE 19850-5019