Set a field to blank or null?

Need help Database
1

Elementary question. I have a field that is of type User. There are times that it will be null or blank. If I need to remove the current User and add a blank, how do I do that? I’ve tried
= “”
=NULL

I know the answer is probably obvious and easy, but I can’t seem to find it. Thanks,

2

Have you tried this?

user

3

That’s what it’s set to now. I should have thought of screenshot to show! It doesn’t work. It keeps the previous value.