Is it okay to install curtains after the new house is moved?

Yes, but this step should be completed after you finish decorating, otherwise it will be inconvenient and dirty before you decorate the curtains. In this case, it will be counterproductive. However, if you don't need to decorate or have already decorated it, you can install it and it will be fine when you plan to move in. This is nothing special, mainly for your own convenience.