Having trouble with the menu and editing it on template used

please move this if it’s in the wrong place!

I would love some help i’ve found some really useful posts in here but can’t seem to get to where i need to be.

i’m using this template Clark - Portfolio HTML5 Responsive Website Template trying to build my site, and i’m having trouble with the menu and editing it - https://www.masonbrownlow.studio/

i can’t seem to edit the button to 1. change the text fields in the menu and then 2. update the links

any help would be much appreciated many thanks