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

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
How to install/add pluginsHow to upload a custom resource pack