i have the same lcd. the csel1 is actually ur PSB. and u may connect it to analog pin 0. mine works like that
let me know if the info helps. i usually find most replies useless as people talk about something else in the reply rather than answering the question >:(
this is my first reply to someone in 1 year :
oh and btw, VSS is ground, and Vdd is 5v or 3.3v pin on ur board. goodluck