Make a solid template of the bolt holes & PTO shaft hole
Slip this over the old PTO shaft and mark the holes
Remove the old engine, fit the template underneath the engine then check that the new holes will not cut through anything before drilling them.
Drop engine into position loosely do up bolts then work out how the wiring will run and what you will need for control cables.
Remove the choke & throttle controls the wires usually are replaceable so work out what length you will need then either buy some Bowden cable or go to a mower repair shop and ask them to fit some cables to the new length
I charge $ 10 for this, including the wire
Go to an Auto shop & buy some plugs & connectors
Usually I advocate cutting the wires off your old engine as long as possible then use these loose ends to fit a generic plug then cut the plug off the new engine as close to the plug as possible then fit the other end to the engine wires.
Check the connectors first as some will pull out of the plugs once the barbs are depressed and some don't, but if they do it saves you a lot of crimping.
Because I am a belt & braces type of man I slip a short piece of heat shrink down the wires before I crimp the wires then bring it back over the crimp & shrink, thus if my crimp is not as good as it could be the joint remains sound.
IF the wire colours are different I try to use heat shrink of the came colour as the other side of the plug which reduces confusion.
Just be 200% certain that you do not accidentlally hook the solenoid wire up to the magneto because if you do you will be buying another new Preditor engine as you will cook the magneto trigger chip and there are no engine parts available for this engine which is one reason why they are so cheap.