I have an 81 Chevy silverado that won't start an I believe it's the ignition. How can I bypass this an get the truck t start?

If it's a crank but won't start problem:

. Remove and fully charge the battery. Most auto parts stores will do this for free.

. Check all under hood and under dash fuses with a test light or multimeter.

. Check for spark. If it tries to start but doesn't, replace the Ignition Control Module (ICM).

. Check the ignition switch for wear, pitting, or melting, after disconnecting the negative battery cable, if you suspect the switch at all.

Never try to by-pass anything!

I think that is old enough to Hotwire the old way, Jump Power to the coil, and a screwdriver at the solenoid.
It may help narrow down, and verify starter and solenoid are not your problem.