Step 1: Google "Discord framework {insert language}" (Would be C# for most of you)
Step 2: End up at this repo:

Step 3: Install it in your project, preferably via NuGet
Step 4: Go to samples;

Step 5: Use "commands-framework" example for commands, such as /online
Step 6: Use webhook example for posting event announcements.
Step 7: ???
Step 8: Profit
Alternatively, if you don't want commands, you can just send HTTP requests to webhook.