I'll give it a shot
So, at the very top of this page above the "The Cathe Nation Forum" heading, you will see several grey tabs... the forth one over from the left is called "Workout Manager". If you move your cursor over it you should be able to click on it and open the Workout Manager (WM) link. This should open a new window. I believe to log in you just use the same user name and password you use for the Forums. if not, it will prompt you to create a logon and password. Mine is the same, so it does not require you to have or create a separate one.
Once logged into Workout Manager, on the left side there is a list under TOOLS. the first tab is One Rep Max Calculator. click on this and it will open the 1RM testing details.
This is where it gets a little cloudy for me as well. You select either an specific exercise or a disc from the STS series and it will bring up a list of exercises that will need the 1RM test calculated for what weights you will need... read through the explainations on this page and go from there.
Also try this link where Cathe explains the whole STS system and what is required. it has a section on the 1RM too:
http://www.cathe.com/STS-FAQ.htm
one other thing... there are also some exercises such as push ups, pull ups, superman's etc, that you can not do a 1RM test on because they do not require you to use any weights. Therefore if any are on the list and you would normally not use any dumbbells or other weights, you can just skip those.
good luck & ask any other questions as needed... hopefully this will give you some additional help in getting into the 1RM location and beyond... if you need more assistance, there is always someone around to give a helping hand
I haven't actually started the 1RM testing yet, but will be doing so shortly. I'm sure I will have lots of questions at that time, but apparently they planning on giving a video tutorial on each of the exercise moves, but that is probably a ways out until after they finish STS.