1) Bring up the Pause menu by Pressing ESC
2) Go down to Profile, click that
3) Look for the button titled “GLYPH” and select it. You should end up at a screen that looks like this:
This is where you can view, buy and equip different glyphs. To equip a glyph, simply Select/ Left click it. You should then see your glyph in the top left corner change to reflect this.
Voila.