Note: Before you read all this, I’m assuming that your mod is a map created in the scenario editor, rather than a random map script? If it is, read on.
Okay, do you know how to open the mod manager? Under settings there should be a mods option. Open this. It’s easiest if you subscribe to a mod for this next part, so if you haven’t, I might recommend small trees as something to subscribe to. Once you have downloaded a mod, now go over to the “My Mods” section. In there, all the mods you are subscribed to should show up. Click on one of them, and click the “Open Directory” button. This will open a file path for a subscribed mod. I think it should be something like Mods > Subscribed > Your mod or something. If it is, go back to the point where you are in the folder “Mods”. One of the subfolders should be “Local”, click it. If you can’t find it, just go back a few more folders in the directory and search for local. Once you find the local directory, open it, and create a new folder inside it. Give it the title of your scenario or map. Then, open that folder, and inside it create another folder. Give this the title “resources”, spelt like that. Inside that, create yet another folder, this time titled “scenario”. Now it is set up. Keeping this tab open, go back to the original game. Open up the scenario editor, not an actual map, just the large database that lets you select and manage your scenarios. In the bottom right there should be a button “Open Directory”. Click it, and it will open up a folder with all your maps/scenarios in it. Select the one you want to publish, and copy it. Now paste it into the folder we just created before, the one titled “scenario”. Now, go back to the game, and open the mod manager again. This time, go the the “My Mods” area. Near the bottom should be a button that says “Import Local”. Click it, and your map mod should appear. Select it, and press publish, then wait for it to be searchable in the mod manager. I really hope that A) That all makes sense, and B) It’s accurate, because I did it all from memory. Anyway, good luck! 
Also, you could have also posted this in either the AoE2 DE Mods section, or the Ask for Help section, but this is fine for now. Welcome to the forums.