Blenders latest version can be downloaded at https://www.blender.org/download/
Please keep in mind that Blender 4.0 and higher have have some big changes. Some names and options might be different from 3.6
Installing the add-on
Open blender and navigate to edit>preferences. (CTRL + ,)
This opens the preferences window.
Click on Add-ons and then select install.
Navigate to the zip you downloaded from Gumroad and either double click it or press the install Add-on button.
Edit>Preferences>Add-ons>Install
Blender might freeze for a little bit while its unpacking the zip file in the add-on directory of blender.
After the installation is complete the add-on should show up.
We can now enable the add-on by pressing the checkbox left of the add-on name
Enable add-on by clicking checkbox
When the add-on is enabled it should display all the add-on preferences for UniBlend
