So I want to start off by asking how well you considered the idea of underwater creatures using electricity. I don't think that it is actually possible to generate and use electricity underwater unless you previously developed insulation techniques. The extreme conductivity of the water makes any early experimentation almost 100% lethal. But now that I have that off my chest, I will continue by answering as much as I can.
The big stumbling block in the development of a civilization is probably the creation of manufactured metal goods. After that, everything is easier. Thing is, octopi don't have bones. And bones are preferable for using human-style tools. So The octopi will probably need to make small tools with multiple purposes. As I said, though, processing metals for tools is very important, so they will need forges. Now, you can't easily build a fire underwater, so I suggest making a forge, which would be a centrepiece for this kind of civilization, on top of a volcanic vent. This kind of thing would certainly be anchored.
Another highly important building is a place for octopi to sleep. I imagine that with the harder life the octopi are doomed to have, materials and food are generally shared, so living spaces can be confined to a place to sleep. But since octopi are invertebrates, all you need is a large object with lots of little holes, some bigger to house families or mating couples. I think a basic chunk of coral would do just fine. A reef would also provide food, so we have that problem solved as well.
Having very little waste and with pooping in the ocean being no problem, no sanitation department is needed. Neither is transportation for distances of under a few miles, as swimming outdistances most vehicles quite efficiently.
Cultivation and farming underwater looks a lot like it does above water. Scared away predators to the farm fish, cage or otherwise enclose said fish, let kelp grow and then harvest it. As for distribution, rotting is slower in saltwater, so a hollowed out boulder or some such should do, plus you can supplement your diet with passerby fishes.
Transportation long distance seems somewhat important. Since buoys are moved by both current and wind they could make excellent vehicles when properly piloted.
As for building materials, I would say to just use coral and rock. "The elements" are a lot less harsh on your stuff down here, so specifically manufactured building materials or cement are unnecessary.
Another thing going for our octopus friends is their squishiness. Doors can be only centimeters across , rooms incredibly small as the octopi don't really need much as they are, and of course safety measures are almost irrelevant, considering how easy it is to rebuild and how hardy octopi happen to be.
So while I know this isn't the question, I don't think that without fire, wood, or electricity, octopi could actually reach human levels of technology. But the nice thing is that their infrastructure would be pretty simple, as they are already a wonderful evolutionary model.