dmu kinematics

[enpa28]

Hello everyone, I created a mechanism with 3 degrees of freedom to which I assigned a command each.
Now I would like to create a law for each command, but when I open the formula editor, I don't see the time parameter. Can someone help me? ?
Thank you.

 

[janlo1986]

click the icon at the top left of the formula window and you should appear (in the middle column) all parameters