First you select the note you are interested. You will then be shown what the note would look like on the staff for each string. Select the note from the 6 presented, and it will show where it is on the fretboard.
While learning guitar tab is easy, it’s also cheating. Don’t get me wrong, I spent a lot of teenage years playing tab, but it didn’t do me any favors as far as theory. It is useful to know that you can play a C on all 6 strings, and vital to know that for improv. However, the C on the third string is not in the same octave as the C on the first string or the C on the sixth string.