Datapacks normally use something called functions, which run every tick, and can cause a lot of lag. It's recommended to find a plugin alternative whenever possible.
A datapack is a .ZIP file that you can use to customize your Minecraft experience without using mods.
Installing a datapack is quite simple. Once you’ve downloaded the datapack you want to head over to your server management tab.
Now go to your server and open “file management” then open “file explorer” in the dropdown menu.
Select the world you want to install the datapack onto.
Open the folder “datapacks”
Click the upload button in the top right corner and select upload your datapack.
Now restart your server, feel free to open a ticket if you need any assistance.