To add a note to your map in FormSketch, select the Note icon in the menu at the bottom of the grid. This will add a 'Post-it note' style note to your map.
You can select the size of the text for the note, the font, the alignment for the text within the note, and the colour of the note.
The sizes to choose from are Small, Medium, Large, and Extra Large:
There are four fonts to select from:
There are three horizontal alignments that you can select, which will determine where in the note the text will display (Left, Centre or Right:
There are also vertical alignment choices that can be used, so that you can have the text in the top middle or bottom of the note by selecting the vertical alignment and selecting the preferred alignment (Top, Centre, Bottom):
Last but not least, there are 12 colour options to choose from for your note, as well as the Opacity option, which will allow you to either have the note semi transparent or solid colour: