This is how you can generate/compile forms using adadmin:

Sign in into your Linux OS as Oracle user.

On Linux prompt enter:

cd PROD
cd apps
cd apps_st
cd appl

. APPSPROD_linux.env (Source environment file)

adadmin (This will launch adadmin)

Answer adadmin questions as follows:

Hit Enter 5 times to accept default values.
Enter password for System account.
Enter password for APPS account.
To generate/compile applications forms, enter 1 then enter 2
Hit Enter 5 times to accept default values.
For question "Choose list of products" Enter ar.
Hit Enter 3 times to accept default values.
The compilation will start.

Also recompile all invalid database objects using adadmin utility.