How do you resize a GUI to fit a user's screen?

I tested an announcement command on my server, while my computer had a good size, the GUI covered up my phone, not sure what to do in this case

because you ui doesn’t anchor that well…
if you want your ui fit well in any device you must make the offset zero on size of the gui
and try to re size it on other then offset

How would I make it anchor well then? Would I need to use a script or could I do it right from the properties?

you dont need a script to anchor the you ui. all you need to do is go to your ui properties and find size and click the xy thing and click more and you will see offset and youtry to make offset thing turn it into (0) and try to resize it with out using the offset

Using the term “anchor” for the UI doesn’t really make sense.

You need to make sure your UI’s are set in Scale.

When dealing with UI, your position and size will be in the same format:
{0, 0}{0, 0}

You must have the info in the first digit of both groups. Something like:
{1, 0}{1, 0}

Would fill your entire frame. Scale details are relative to device and the parent of the Frame/TextLabel/Any UI element.

Here is more info if I explained it poorly: