I bought Masterstudy template.
I click- Demos instal.
I choose a demos template.
Fault - the site remains with the previous demos template.
How to change demos template?
I think you have to set everything (menus, widgets, front page …) manually for the new demo import.
For any technical query about theme functionality the best choice will be contact theme Author and let them know How to Contact your purchased theme Author, theme author will be happy to answer your query.