1. I would find it easier to first remove the plastic cowling beneath the windschield. Removal of the cowling makes it easier, for me, to reach the rear of the engine. This is covered in chapter 13 (IIRC) in Haynes.
2. Remove all spark plugs. To avoid the possibility of getting shocked, disconnect the ignition pack. ... of course, you could just choose to avoid the spark cables instead. Pull the fuel pump fuse/relay or somehow disable the injectors.
3. During the compression test, intake air must be free to the engine. There are several ways to achieve this: ...(a) have assistant hold gas pedal down ... or, (b) prop the throttle "open" somehow underneath the hood ... or, (c) remove the air filter cartridge and throttle body this is my favorite. Allthough I have also removed the upper intake manifold if I'm about to do upper engine repair.
4. Conduct the test. Depending on what kind of tester you have, insert (screw) test prong/tip into spark plug holes. Keep tester in place while the engine is cranked several revolutions until the tester gauge reaches its maximum reading. Record gauge reading. Reset gauge and move to next cylinder. After all are completed, review readings ... retest any cylinder that has readings you suspect are in error.
Depending on engine condition and tester, the readings will be approx 175psi. Piston ring and valve wear will make a reading lower. Excessive carbon build-up will make a reading higher. You hope the highest reading will be no more than 20% of the lowest reading.
Some folks recommend taking a second set of readings after dropping a few drops of oil into each cylinder. The idea is to wet the rings with oil to identify worn rings versus worn valves. I do not recommend this procedure! It is indefinite ... you are never sure if you have the rings completely wet, but do not have excessive oil in the cylinder. All it takes is one experience of forcing oil back into the test gauge and you will do this procedure no more. Ask me how I know!
Happy hunting!