Hello. I'm trying to figure out how to add a dotted quarter note. Thank you.

Welcome to the forums.

Could you provide a little more information on where you wish to do this?

If this is using the notation editor, then you need to be in edit mode which is shown below. Then you can mouse click on the stave at the appropriate point and enter the note. To shorten it, insert a rest after that point at the correct position.

Either by inserting a rest, or another note, you let the program determine how long the prior note will be.

Or, in Editable Notation Mode, you can right-click on a note and use the numbers to alter the duration.

You can also change the position and duration of a note in the Piano Roll Editor. To enter a note, hold the Shift+Ctrl keys. The cursor becomes a pencil. Click where you want the note and it is inserted with a duration you have selected from from the "Dur" drop-down menu, and on the channel selected by the "Chan" drop-down menu.

In short, when you add a note, you don't tell BIAB how long it is. You use the next note (or rest) to allow the program to then determine how long the first note will be. Then, if that needs tweaking, you edit it in one of several ways.

This may seem odd to those of us who use dedicated notation programs (and I've used almost all of them). The BIAB way of writing notation is my favorite of all, by far. It's just different and takes a moment to get used to. I often write a melody in BIAB even if it is destined to wind up in another program.