Susan!
The aquarium "cycle", ammonia->nitrite->nitrate, is a process of creating enough bacteria to quickly convert new ammonia rapidly through the the changes so that you never detect ammonia or nitrite. The initial cycle (usually induced with live rock but there are several ways to create the ammonia) needs to complete with no, or minimal water changes. You should now be looking for nitrite followed by a drop to zero of both. You will want to continue creating ammonia after the initial cycle to grow enough bacteria to handle the heavy waste (ammonia) load of an octopus.
Once you see ammonia and nitrite drop to zero, you will want to add critters to produce waste and can start your weekly water changes (10% recommended) to keep the nitrate at bay and reduce some of the protein. A skimmer is highly recommended not only for protein but to remove ink before it can become a problem (a water change after an inking episode is still desirable). Sometimes this is done by adding fish (that will have to be rehomed before the main occupant is added) but I prefer to add clean up crew (hermits, snails, serpent stars) and over feed the tank. Because of the heavy waste production of an octopus, we recommend a minimum of three months of actively cycling (continuing to build bacteria).
At the top of the Cephalopod Care forum there is a stuck thread,
Posts with Info for New Octo Keepers, containing links to some of the longer posts and discussions on getting started that may be helpful.