1. Open your project's folder. It should look like the picture below

2. Create a new folder and name it "Plugins" (if you don't have one)

3. Extract the .rar file into the "Plugins" folder. It should look like this:

4. Open Unreal and go to the "plugins" tab. You will find it under "Installed > 2D"  

(Edit->Plugins->Installed->2D)

5. Restart and done! Enjoy and go create some cool games!