If you purchase the xTool Screen Printer multi-color kit, you can find two frame fixing pieces, one for xTool D1 Pro and the other for xTool S1.
This page describes how to install the frame fixing piece inside xTool D1 Pro.
Note: In screen printing, the frame is placed with the front side facing up. You may need to rotate and reflect the design objects based on how you will place your material.
For example, to print a pattern on your T-shirt as follows, you need to rotate the pattern and reflect it horizontally and vertically on the canvas before engraving it.