First, click the Add a Server button on the left under the servers you're in.

Then, click the Create my Own button. Or, if you'd like to use a different template, press one of the other buttons.

Now, click For me and my Friends. Like the last one, you can choose a different option, but I won't be going over how to set them up (although the webhook setup should be exactly the same regardless of what type of server you have).

Finally, name your server and press Create.

Next, click on the icon for the server you just created and it should look something like this.

Now that you're in the server, press on the name in the upper left-hand corner and press the Server Settings button.

Click on the Integrations tab, then press Create Webhook.

Rename your webhook and add a profile picture if you'd like to, then set the channel you'd like it to post in and click Copy Webhook URL and paste it somewhere. Then press Save Changes.

Navigate to the Feeds tab and click New Feed. In this screenshot, I'm creating it in a group I made for this guide, but it's probably easier to just create it in the Default group.

Now, make your feed. I called mine plant.

After you've created it, you should see it on your Feeds page.

Now that you've made the feed, go to the Actions tab and press New Action.

Then, select Reactive Action.

Then, select your feed in the dropdown next to if.

In the dropdown next to is, select less than.

In the text box below that, write the moisture value you want it to notify you at. I used 500, but that was really just a guess. My advice would be to wait until you normally would water your plants and then get the moisture value at that time.

In the dropdown next to Then select send a webhook message. Paste the link you got from Discord in the box under that.

When you've done that, select your feed in the dropdown to the left of value and time. 

Set the final dropdown to Discord Template, fill in the username you want for the bot on the first line in the set of quotes after the colon, and set the second line to the message you want it to send you.

If you want it to ping you, put your discord ID in the message with this formatting <@discord_id>.