Just to draw it out from the longer thread: you can “tenuki” by pressing “pass”.
If the “pass” button is lit up yellow, it means there is a tenuki variation available.
I too find this a common question in my play
I entered it, and you can get to it, by pressing “pass” after playing the 4-4 stone - that’s how you “do” enclosures.
If you play the enclosure using the dictionary and the invasion variations are not there, it means they are not added yet.