This article, part 3 explains the tank installation and final steps.
At this point you should have a working toilet that you could add a seat to and flush with a bucket of water if you had to for some reason.
The next step is to attach the tank to the bowl. Most toilets have a donut washer around the bottom of the flush valve which is located in the center of the tank. This provides a cushion and seals the connection. It may already be attached or it may be something you have to put in place.
Once that is done, gently lower the tank onto the bowl lowering the two or three bolts into the holes provided. Add washers and nuts and then follow a similar process to what you did with bowl. With the level across the tank alternately tighten the bolts while keeping the tank level. If you have followed the advice about the extra nut and washer on the bottom of the tank, this step is real easy. Again, please be careful not to over-tighten. A good snug fit is all you need. Your tank must be level from side to side when you are done. If that requires more tightening of one side than the other that is fine. Unlike the bowl you can loosen and adjust this as much as needed.
Just a few more easy steps
Connect the water supply to the tank valve. Personally I never try to reuse an old supply line. What is $2-3 more when you are saving $250-300? I also use those flexible metal braided connectors. Take note that sometimes the slightly longer model is easier to twist into position than the size you think you need.
Turn on the water, allow the tank to fill and flush. Let the tank fill again and check for leaks. A small leak at the shut off valve usually just means the packing nut (the nut that hides behind the handle) needs to be tightened a bit.
Install your new toilet seat or your old favorite if you must.
For the final step I like to wait a few days. The final step is to caulk around the base of the toilet using a quality kitchen & bath grade of silicone caulk. I like to wait and be absolutely sure that there are no leaks from around the wax ring before I seal the area. It is very rare for there to be one if you followed these directions carefully and that is especially true if there was no wobble or shims used. So please yourself and caulk now if you like.
The final step is to retrieve that tank top and place it on your new throne.
Part 2 explains the bowl installation.
Part 1 covers tools, preparation and old toilet removal.
