In the right-click menu for any of the fields you’ve selected, you’ll see the « Copy ID » option. Click it! Once you’ve clicked « Copy ID », you’ll have the message, user, or server ID copied to your clipboard.
The easiest way to report someone on Discord is to simply tell a moderator of the server that the inappropriate behavior occurred in. If you want to report something to Discord’s own Trust & Safety team, you’ll need to turn on the app’s Developer Mode.