Pack it as a .lkt file¶
A .lkt file is your plugin folder squeezed into a single file, which makes it much easier to share, and it's also what you'll need for the .jar on the next page.
To make one, open your MyPlugin.lkt folder and select the files inside it (main.lua and plugin.yml), not the folder itself. Make them into a zip file, then rename the zip to MyPlugin.lkt.
Before you put it in your plugins folder, move the old MyPlugin.lkt folder out of there, onto your desktop for example. A folder and a file can't have the same name in the same place, so only one of them can be in plugins.
Files inside, not the folder
If you zip the folder itself, main.lua ends up one level too deep and the plugin won't load. Open the zip and check that main.lua is right at the top.
With your .lkt ready, you can turn it into a .jar.