get one’s feet under the table—get settled in:
- It will take four or five months for Greg to get his feet under the table, to understand the enormous number of complex and tricky issues he has to master.
put one’s feet up—relax or take a rest:
- That way I can put my feet up and not think about Christmas at all until a week beforehand, when we put up our decorations.
Note: The expression does not correlate in meaning with the phrase have a knees up—have a noisy party usually with dancing:
- We had a little party for him and some speeches and went to the pub and had a knees up.
See also: put one’s foot down / put one’s foot to the floor.