The first step is to find the correct length – too long, and it will flop around in the biggest gears, and shifting will be iffy; too short, and you will rip the derailleur off the frame! The correct length is just long enough to wrap around the combination of the largest front chainring and the largest rear sprocket, plus one link. You may (should) never ride in this gear, but is is the benchmark.
To remove an excess link, put the chain in a chain tool, with the pin you want to pop positioned so that when you screw the handle in, the pushing pin will press it through the chain, and out the other side.
Unwind the chain tool all the way, and loosely put the chain together n the bike, threaded through the derailleurs, and with the joint at the bottom, between the rear derailleur and the chainring.
The exposed pin must be facing away from the wheel. Slot it into the tool, and gently wind the pin in until you feel it push through the other outer plate. You are aiming to have equal pin showing on both sides. Take the tool away, and check that the new link moves freely.
If the link is a bit stiff, gently flex the chain forward and back, with your thumbs on the offending piece. Gently! It should loosen up.
Screw it in with the chain tool until it clicks, then break the excess bit off with a pair of pliers. Simple.
Powerlinks are wonderful, when fitted correctly. They replace an outer link set with a new pair that is slotted so that you can fit without a chain tool. Always carry one for emergencies, but you can also use one as a stand and avoid all the hassle of chain tools.
Some are reusable – push the halves together to break the chain – but many are not, and they are very width-specific, so a 9-speed powerlink won’t work on a 10-speed chain.
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