Tutorial Video. Step by step below;
1
First Step
Download your desired Datapack from the web. (We prefer using Planet Minecraft)

2
Second Step
Click on the Download Datapack button.

3
Third Step
Login to your Wepwawet Control Panel

4
Fourth Step
Select your Server

5
Fifth Step
Make sure to Turn OFF the Server

6
Sixth Step
Under the General Section, Click the Files tab and select your current world folder.

7
Seventh Step
Click on the datapacks folder.

8
Eighth Step
Upload the downloaded datapack file. (as a .zip file)

9
Nineth Step
Head over to the Console tab and Start the Server.

There you go! You now know how to install a datapack onto your Server