This is the location form and not the right place. Please follow these steps

1) You should right click the Name field and configure dictionary

2) Then on the form that loads, Again configure form layout from the header and add unique field on this form.

3)

4) Add the unique field on dictionary form and check it as true and Save.

Once you do so, the system wont allow a user to enter multiple locations with same name.

Thanks

Please Hit like, Helpful or Correct depending on the impact of the response