+1 to Ramseyneil, and sorry for taking the piss before. My trolling sensor went off incorrectly by the looks of it. I was also slightly concerned if you couldn’t work out what pads you needed, I’d be alarmed at letting you do a safety relevant maintenance job on your bike, but good on you for learning. Maybe this time take them to your mate and get him to show you so you’ll know for future though?
Shimano are dead easy, never had an issue.
1/ Take out the wheels!
2/ using a wide bladed screwdriver (or tableknife, or even better a thin plastic tyrelever*) push the pads apart so the pistons retract into the caliper.
3/ loosen off the bolts holding the caliper to the fork / frame
4/ remove the pad retaining pin (may be a split pin, may be a small bolt) Don’t lose it!!
5/ remove pads and springs, pay attention to orientation and order (it’s obvious enough but worth looking at the old set anyway)
6/ insert new pads and springs
7/ Refit the retaining pin which you didn’t lose after step 4
8/ Reinsert the wheels
9/ spin the wheels to centre the caliper, then pull and hold the brake lever (may take a few pumps to take up slack depending how worn the last pads were and how thick the new ones are). Once they bite, hold the laver so brakes are tight on.
10/ Nip up the bolts holding the caliper. Nip! They don’t need to be monkey tight, and if you do over tighten and strip the threads on your fork you’ll be in a world of pain!!
11/ release the lever and check the wheel spins freely. Occasionally you might need to do 9/10 a few times to get it to centre properly or even ride it a bit with a bit of rub to allow the pistons to even out a bit. If you have massive rubbing, there could be several reasons and with all good intent, at that point if you’re just learning to change pads, I’d get someone ‘qualified’ to look at it.
12/ Don’t forget to do 7/, and recheck it every ride. If your pins goes missing and your pads selfeject, best to not find out on the hoof.