In past I made a FAQ (quite obsolete site right now) because of lot of questions:https://code.google.com/p/pms-exsport/wiki/FAQ
Also I am sure you will find same step-by-step answers in forum or FAQ here.
When you will set PMS correctly and your files have correctly tagged audio/subs tracks, PMS then should respect your settings and enable subs only for audio languages you don't understand (plus it supports FORCED subs which can load subs also for languages you understand but there are parts which are in different lang like latin, klingon....)
Check the linked FAQ.
Also in TRANSCODE folder you can find all the audio/sub combinations so you can easily play option you need. Also there is VIDEO SETTINGS folder (if enabled in GUI) which gives you definitely enable/disable subs directly from your renderer.