How do you install a clutch in a 1991 Acura Integra LS?

This can not be answered easily.

Checkout g2ic.com There are several threads on the process.

In summation you will need to remove both axles, shifter linkage, transmission mount, rear engine mount, engine to transmission bolts, bottom stiffeners, a few wiring harness connections and several small brackets.

Be sure to replace the throwout bearing and have the flywheel machined. A new clutch cable is a good idea since they tend to wear out.