I'm trying to hide two field on a specific layout. I have the hide object when set to : LayoutNames ( "Users" )

wouldn't that hide the object when i'm on a certain layout? in this case, i'm on the layout Users, but it's not hiding the fields. Not sure what to do here.

I'm trying to hide two field on a specific layout … when set to : LayoutNames ( "Users" )

The correct expression would be

Get ( LayoutName ) = "Users"

But if you don't want to show a field based on the layout's name, you could simply not put the field on that layout. “Hide if” normally is used to show or hide objects based on data; e.g. use a single layout that displays/hides fields depending on user name, or privilege set, or entity type etc. 

Thank you eos!

Would not putting the field on the layout work if I'm using a portal?

Well, if it's not on the layout, it's not on the layout – whatever part that may be

IMO, it's better you start from the beginning to describe your setup and what you trying to achieve, so whoever reads this is able to give you informed advice.