Before fitting the new shock, make sure the mount points are all in clean and in good order: no cracks, damaged threads or bad corrosion. Do the same for the mounting nuts and bolts. You can also take the opportunity to give the area behind the shock a good old clean.
This mount has been cleaned and blasted for powder coating, so is pretty clean, but there's some protecting tape still in place that needs to be properly removed. Give the mount a nice coat of copper grease (or your preferred chassis grease), and slide the shock into place, wiggling the swingarm up and down if needed. Refit the nuts and/or bolts, replacing any single-use locking nuts, and torque them up to the correct setting.