Hi ZXRobotum,
the config.json file is divided into multiple sections, one of them is PluginSettings. In this section, there’s a key named EnableUploads which defaults to false.
Here’s what it looks like when you open it:
"PluginSettings": {
"Enable": true,
"EnableUploads": false,
[...]
In orde rto enable the plugin uploads, you would have to change the value false for the key EnableUplodas to true with your favourite editor, then save the file and restart the Mattermost server.
Let me know if this helps or if you encounter any issues.