Click on F3_Add_Text.
In the text options dialog box:
- enter a text string
- select units
- enter the height of the text
- enter the line width of the text
- select a text layer
If you selected the BOTTOM side, check the box MIRROR (6).
If you placed text inside a copper area with the hatch style of EDGE or NONE, you can use the NEGATIVE_TEXT option (7) to draw the text as a hole in the polygon.
It is useful to know that when a text string matches the name of a network, that network will be half-highlighted.