In-text citation wont change from (5) to [5] - How to get square brackets?

I want square brackets to appear around my in-text citation. Right now, the style which I downloaded has ( ) brackets, so I changed it to []  brackets, but it wont update.

I have definitely made the amend in the right part of the programme.

(I know that on the left-hand side there are loads of options.) This is where I made my amend:

Citations > Templates

I dont know what Im doing wrong. Am I supposed to use a “foced separator” or something?

This is the style which I downloaded:

I would really appreciate it if someone could help me out

Thank you