I dont usually use the minehut market for plugins as you can usually get all the plugins there easily on SpigotMC, a more reliable source. Here's how to download plugins from SpigotMC.
1. Download the chosen plugin from Resources | SpigotMC - High Performance Minecraft
2. Go to your minehut server's file manager
3. In the plugins folder, click "upload file"
4. Upload the .jar file you downloaded and restart the server
Uploading plugin files are much better then downloading them from minehut's market in many ways I won't get into right now. Hope this helps!