@arkxell
You haven't explained what you have tried to do, and what has failed...
Here's some simple steps...
Possibility 1
You already have an earlier version of SketchUcation Tools installed.
Open the ExtensionStore³ dialog, find the tools and click on the Install button.
When it completes, restart SketchUp to sync everything.
Possibility 2
You don't have an earlier version of SketchUcation Tools installed.
From our PluginStore, find and download the SketchUcation Tools RBZ file.
Open the native dialog in Extensions > Extension Manager: click the dialog's - Install button, navigate to the downloaded RBZ file and it will install.
When it completes, restart SketchUp to sync everything.
To license an extension you need to have bought a license and kept it somewhere safe on your computer.
You can validate a license in the dialog which opens in the particular Extension's submenu - usually under Tools.
There are more detailed pages on our site about this...