Samsung SL-M2020W-XAA - Manual (Page 34)

Media and tray
34 2. Learning the Basic Usage
5
Setting the paper size and type
After loading paper in the paper tray, set the paper size and type.
To change the paper setting set in the machine, from the Printing preferences
window > Paper tab > Paper Type (see "Opening printing preferences" on page
36).
If you want to use special-sized paper such as billing paper, select Custom
in the Paper tab in the Printing Preferences (see "Opening printing
preferences" on page 36).