Can't get plugin to work

[Charity_Diamond]

I'm trying to get the keep inventory plugin to work, and I don't understand what to do or if I'm doing something wrong or what. I've never done this stuff before, and I'm trying to get it to work for me and a friend. In the files section, in the plugins folder, it has the keepitems.jar but has a crossed O through it. I can't use the commands in-game, but it says that it's installed and has a little * beside the name. I don't know how to make it work. Please help? 

[_Tarna_]

Make sure to restart the server after getting the plugin so it will generate the plugin's folder with its config and everything. Also can you explain on more whats not working? You can view the plugin's spigot page here and it'll show you on how to use it and everything. - https://www.spigotmc.org/resources/keepinventory.1638/

[Charity_Diamond]

This is what it looks like in the folder and in game. I've restarted the server several times and it never works. I type /keepitems.keep and it tells me that it's an unknown command. I do /plugins keepitems.keep and it doesn't work. I would move the actual file into the folder for the server (according to some YT videos that's what you do), but I don't have any files on my computer. They're only on Minehut and I don't see anything that says *download.*