How do I alphabetize my Photos Albums?

I'm not sure what you mean by alphabetize?

Do you want to sort the albums alphabetically?

If your albums are in a folder, you can select the folder in the sidebar and use the command "View > Sort > Sort by Name".

If the sidebar is hidden, you can click the "Albums" tab and also use the command "View > Sort > Sort by Name" to sort the albums not in a folder.

In the sidebar Control (right) - click on the right side of the Albums title (over Hide) and select Sort ➙ By Name in the contextual menu. That will sort the albums by title:

First boot into Safe Mode, Mac OS X: Starting up in Safe Mode, and try from there. Then reboot normally and try again.

As described in the second part of my reply. If the albums are not in a folder, you can sort them alphabetically in the "Albums" tab, but not in the sidebar.

Good to know, OT!
Something must be broken in my Photos Library. Ctrl-clicking on the Albums title does nothing in my Photos Library since macOS 10.12.2. Time to trash a few preferences files! 😁