Forgot admin pw on initialization/install RH 7.3/PGSQL7.2

I made a dumb mistake, and forgot to write down the autogenerated
administrator password when I first started the Postgres database on
RedHat 7.3. I'm having a hard time finding information on how to do this
online, and it's a tricky term to search the archives for, as well.

I don't have any data I need to save (obviously), so how do I nuke the
data and configuration (particularly the admin user) created during the
initialization startup script? I don't want to go randomly deleting
postgres' .conf files when I don't know what I'm looking for.

Thanks.