You can't increase the font size with your printer. It does not have that option. You need to increase the size from source of which you are getting the data from before you print
Example: if you wanted to print a word document, you would go to the taskbar on the top and change the font settings prior to printing.
Or do this
Open up the what you want to print
Left click and highlight either part or the whole area you want printed
Right click the highlighted area and click print preview
Change the box "As laid out on screen" to "As selected on screen" doing this will let you print all or part depending on what is highlighted
In the box Shrink to fit, change it to increase or reduce the size font that you want to use
Click print, and go to Page Range, and make sure you add a dot to SELECT
Click print