A figure must be selected to alter the Font Size of entered text. To access the text attributes for a selected figure(s):
Press on the Text option to open the Text Panel.
To alter the Font Size:
Tap on the "Up" or "Down" arrow buttons in the Text Panel underneath the Font Size heading to increase/decrease the size by increments of 1 or press on the number field to enter a new size with the text editor.
To close the Text Panel, tap on the Hide Sidebar Button located at the bottom of the sidebar panel.