You can link your checking account to your IBKR account for the purpose of transferring USD denominated funds between the two accounts via ACH. This process requires that you first create a banking instruction and verify your bank account. The steps for creating an ACH instruction are provided in the Interactive Brokers Knowledge Base. Keep in mind that all account users with access to funding will need to be two-factor authenticated.
Also note that deposits made via ACH are subject to a 4-business day hold before being credited to your account and, if withdrawn, can only be withdrawn to the originating bank for the 44-business day period thereafter.