The Prepare To Restore Step, BMR refers the configuration and then inserts the relevant drivers inside the SRT. As a user you do not need to add them in the SRT specifically.
I believe you have used the Driver Package Wizard to specify the new drivers and they are now part of the BMR driver database. Now all you need to do is select the right configuration and right SRT and then perform Prepare To Restore on it.
This will generate a Network Boot ISO. You can also use the SRT Wizard to create Bootable CD-Media ISO too.