Method 1: Theme Installation via Admin Panel
First of all, you need to download the DiviBest_Lagoon.zip file and unpack it somewhere on your machine
Now go to your site Dashboard > Appearance > Themes and click on Add New Theme

Now click on Upload Theme

Choose the zipped file named lagoon.zip that you have unpacked from the downloaded DiviBest_Lagoon.zip file and click on the Install button, then wait for the installation process to complete.

Once done, for the final step click on Activate.

Method 2: Theme Installation via Manuel FTP Upload
If you can’t install the theme via the first method, you can install manually by doing the following:
- Log in to your server using your FTP client ( FileZilla, Transmit, etc )
- Unzip the lagoon.zip file you’ve extracted from the DiviBest_Lagoon.zip file.
- Upload the extracted theme folder into wp-content > themes
- Activate the newly installed theme in Appearance > Themes
- Done