Step 1: Take old skimmer out.
Step 2: Put new skimmer in.
Step 3: Turn new skimmer on.
You might experience water/bubbles overflowing the collection cup at first, but it will break itself in and start pulling gunk out of your water column within a few days. My Reef Octopus had a half cup of skimmate within 24 hours. Good luck. Please post results!
I have tried the traditional way of letting it overflow until it breaks in, and also runing it in 50/50 water and distilled vinegar. I have found out that running it in the vinegar solution helps it break in faster. I now let any new skimmer run for a few hours in water and vinegar then rinse it in some RODI water before installing in the sump. I have seen results vary from a few hrs to a few days but still better than having it overflow for days or weeks.
Get a 5 gallon bucket to put the new skimmer in. I like to put some vinegar in the bucket along with some ro/di water to get off some of the oily residue. Then I will put some saltwater in the bucket and begin the break-in period. Once broke in, make the switch.