How can I change the way phone numbers are entered?

I would like my phone numbers to be entered as 123.456.7890

Can I create an entry like that?  ___ . ___ . ____

                                              box . box . boxx

Yes, you can do that with the help of Input Masks.

Select the phone number textbox on your form builder.

Click the Properties button, go to the Options tab then find Input Mask option and switch it to ON.

On the input mask type ###.###.#### to achieve what you want.

To learn more about Input Masks, check out this guide: Getting Started with the Basics of Input Masking