Hi,
Before activating the premium theme, if you have any available data, please take a backup of your website.
To install the theme, please refer below to the documentation for a better understanding.
Here is the link: https://ovationthemes.com/docs/ot-construction-firm-pro-doc/
We hope this gives you the information you need.
Please let us know if you need anything further and we would be happy to help.
Many Thanks