Spigot is a server type that must be compiled before use. In the spigotprofile menu there is a button besides the version you want that say “build spigot / craftbukkit”.
After the server jar is built you need to copy it to the minecraft server directory. This is done with the “copy to server” button.
There was a short while problems with building thorough MineOS, this has been resolved. Please check if you have upgraded your MineOS version. See more here: How to properly update mineos-node. Do not forget to restart your mineos service after updating.