Now that you have the credit card sized BTS ticket proceed to the metallic barriers. Choose one of the ones with a big green tick showing. This indicates it's an entry point. The Red X's show exit points coming from the other side.
Place your ticket into the lower slot on the barrier. The ticket will be taken in and pop out on top as the red barrier pulls back. Take the ticket back and quickly walk through. Don't delay too much as the barrier only stays open for about 2.4 seconds.
At the back of the BTS ticket is a small map showing you all the BTS stations. Helpful if you forget the direction you are going.
Proceed up or onwards to the platform you need. The platforms are generally named with the last station on the line. So if you need a station before that one, then go to a platform with the last name on that line.