I'm running this plugin on a Paper MC server.
Download the jar file from GitHub here. You'll end up with a file that looks similar to this: DiscordSRV-Build-1.26.0.jar
Place the jar file in your MC server's plugins directory.
Restart the Minecraft server. This will create a new directory called DiscordSRV containing the config files.
Open the main config file (config.yml) to prepare for configuration in the next section.
Navigate to Discord's Developer Portal
From within the Applications tab, select New Application, name the new app, and select Create

Select Bot from the App's side menu then select Add Bot

With a bot created, inside its settings, copy the token (you may have to use the Reset button to generate a new one)

Copy/paste the token into config.yml
BotToken: "MTA2Mjg4NDc4MzUNTg3NDg5Ng.Go3cDt.HdEqGfvxKy3BETvOrcQfx7t2x51FTSiSvKComg"
Enable both SERVER MEMBERS INTENT and MESSAGE CONTENT INTENT

Invite the bot to your server by appending the new application ID to the following URL. (App ID is on the General tab of the app)
https://discordapp.com/oauth2/authorize?scope=bot+applications.commands&client_id=