When you find one that needs to be adjusted, simply click on it to "move it" into the selection spot - between the two lines as shown here with the letter "Q". The character that is between these two lines has the focus of the program so you can move it up or down with you mouse and this new location, the baseline adjustment for this letter will be saved in your font file.
Note - you will find that mapping fonts is really fast but having over 100 fonts in your list might be a little bit hard to manage. There is no limit to how many you can have, but some people like to map and adjust the baseline for the fonts that are their favorites. Ones that they use quite often.
But because it may be easier to map an alphabet and delete it after creating their design that says "Congratulations!" in this font....you might only check to make sure that the letters that make up "Congratulations!" have the correct baseline -- because you're going to delete the font afterwards anyway to make your list more manageable! No need to make sure the letter q is in the right spot, right?