How to add Addons to a Minecraft Bedrock Server
Minecraft Bedrock has something called "Addons", These are similiar to Mods which you would get for the Minecraft Java Edition. These Addons can add new content into Minecraft Bedrock edition, in this guide, we'll be covering on how to add these addons to your server.
Before we begin, it's Impotant to note that Minecraft Marketplace addons will not work on a Minecraft Bedrock Dedicated Server, you will only be able to use Addons from CurseForge
Getting the Addons loaded
1 You'll first want to head to CurseForge and download the addons of your choice.
2 Now, you should have the addons downloaded, navigate to where your downloaded files are.
3 Next, you'll want to open up Minecraft Bedrock Edition.
4 Head back to your Downloads folder, you're to Double-Click or Open the Addon.
5 You will get a notification in Minecraft Bedrock saying the addon has been Imported.

Enabling the Addons
Now that you have the addons imported, you'll now need to enable them in your Minecraft Bedrock Edition World.
1 You'll now want to navigate through the Minecraft Bedrock Menu until you see the Worlds screen.
2 You'll want to Create a New World, and head to the Resource packs and Behavior packs, you'll want to click on Available and you should see your packs there.

3 Next. click on the Activate button to enable the packs.

4 You should now join your world atleast once, just to make sure everything is loading as it should be.
5 Once everything is looking good, we can now proceed to get the addons on the server.
Uploading Addons to the Server
We're now going to begin the process of getting the Addons uploaded to the server.
1 Open up the Run App on your computer and put in the following %appdata%/../Local/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/minecraftWorlds

2 This should've opened up the worlds folder on the computer for Minecraft Bedrock, you'll want to look for the one with the most recent Date modified.

3 Next, you can rename the world to "world", or something you prefer.
4 You will now want to make a Zip Folder and put the world folder into it.

5 Now, head to the com.mojang
folder.

6 Look for the behavior_packs
and the resource_packs
folders, you'll want to open both of these folders.

7 You will want to open both of these folders, within them you should see your behavior_packs
and your resource_packs
in their respective folders.

8 Zip up the Behavior Packs and the Resource Packs you wish to use in their own zip folders.

9 Login to the Kinetic Panel
10 Head to the File Manager

11 Click on the worlds
folder and it should open, in some cases you might see the default world called "Bedrock Level", we can ignore this.
12 Upload your world.zip
that you zipped. Once it is uploaded, Right-Click and select Unarchive

If the world file is too large, you may need to use SFTP.
13 You should now see the world folder there.

14 Now, go back a page in the File Manager and open the server.properties
.

15 Look for the Level Name
category within the file, and change this to what you named your world file. Then, just save the file.

16 Head back to the File Manager main directory & look for the behavior_packs
and the resource_packs
folders.

17 You will wan't to upload the Zips of the Behavior Packs and the Resource Packs in their own correct folders here in the File Manager.
18 Once you have them uploaded, you can Right-Click & Select Unarchive

Common Mistakes
From there, you should be all set with the Minecraft Bedrock Addons working on your server, just join the server & make sure everything is there. If they are not working, you can refer to some tips below.
Minecraft Version - Always make sure the Addons you are using are for the version that your server supports, if they are not, they might not work.
World Not Working - It's important you have the same Level Name
as the world you uploaded, as the world will have the packs loaded.