Basically, you just hit [STO][1] and that will store the number in the 1 spot, [STO][2] and that will store it in the 2 spot, etc. To pull it up (to recall it), just hit [RCL][1], or [RCL] and whatever spot you are trying to recall.
Note, in order to store a number properly, you must have hit the equal sign first before doing the above steps. So for instance, at the end of a calculation, you hit [=], it gives you the number, and you want to store it, so you hit [STO] and then a number. This will work fine.
What will NOT work fine is typing in the number 675 and then trying to store it without first hitting the equal sign. The only place this might actually affect you use the “squared” button, because although it performs a calculation (i.e., it squares the number you had on the screen), you have to hit equal for it to register that that’s the number you want to store.
I would strongly suggest searching on google to find an e-version of the user’s manual that comes with the calculator. I kept mine and it has been invaluable. You don’t want to be trying to figure out how your calculator works during the exam, and you also don’t want to wast time doing things the long way if there’s a short cut that you just don’t know about.