You will find everything you need for subtitle display at
Dr.Mabin's UnOfficial TCPMP site. Be aware that there are some major problems with the subtitle plugin, it supports only SAMI subs so you will probably need a subtitle converter like
Subtitle Workshop to convert your existing subs, it doesn't display all characters correctly which might be a problem for non-English/non-Korean people and I am told it can be unstable when using the Intel 2700G video driver.
I hope I haven't put you off too much because it really does work just not as well as native subtitle support (which is coming soon - hopefully).