If I'm in the main map area, I can tap-and-hold over a square to open the advanced menu. In this menu, I can show the terrain info, and if there's a unit standing there, I can open the civilopedia for that unit type. I did some reading about the SDL client on a computer, and found that when you're in the screen that allows you to choose what to build, you can click on any building/unit with the middle mouse button to open the civilopedia entry for it. I tried the tap-and-hold in that screen, but it didn't seem to work. Is there anything that can be done on a tablet that typically emulates a middle-mouse click? If there is, then that might work here.

As for how I would like to access it, I suppose perhaps tap-and-hold on the building, or maybe a keyboard shortcut if that's easier.