Are you an experienced Finale user?

I am not sure how detailed directions you need.

Depending of the positional requirements (vertically and horizontally) I would add the brackets with the Articulation Tool or the Expression Tool.

You can (in the Shape Designer) create the brackets as shapes, and use the shapes as shape articulations or as shape expressions.

With the Shape Designer you have full controll over the layout details, such as line thickness and length.

By The Way:

It may be useful to remember that the height af a staff is 24pt. (24 Points)

Hence the distance between two staff-lines is 6pt.

And the height of a scale step is 3pt.

Also, in the Engraver Font there are some ready made brackets which may - or may not - be sufficient for your needs.

Here's a good discussion from the old Forum.

https://forum.makemusic.com/default.aspx?f=5&m=373713

My favourite way is to create articulations using glyphs from the Engraver Font set. I can set them to position automatically, and set Articulations as an item to be avoided in Music Spacing, and thus always have enough room for them without manually respacing. I hate doing that.