Sorry OP, I disagree, feedback essential so that we know that we aren’t wasting our time trying to help you. You still haven’t answered “does your preamp have a HT pass through?”.
In laymans terms for a surround system you’ll need something to split the signal into channels (preamp-processor), provide amplification to each channel, followed by a speaker per channel. A HT (home theatre) pass through on a 2-channel preamp allows use of your 2-channel speakers in your surround setup.
If your 2-channel preamp does NOT have a HT bypass feature, I suspect your only option is to directly wire your 2-channel speakers like the rest of the surround speakers from your surround-preamp-processor.