You gotta disolve 25g (35g if you weight more than 100kg) in 50ml (65-70 if 35g) of water, and drink it as it was a shot, real quick.
You have to be fasted 8 hour (2 hour liquid fasting).
You need to have a second backup glass, prepared identically, in case you vomit the first one, you drink the 2nd one.
You have the entire protocol in the PPH book or in several threads in the forum.
If you are CTBing tomorrow, I wish you good luck, and I hope you find your peace!