Change the subreddit field to your desired source, then done! /r/all by default. Change for less notification spam.
If
New top post in subreddit
This Trigger fires every time a new post becomes one of the ten top posts in the subreddit you specify.
Then
Send a notification from the IFTTT app
This action will send a notification to your devices from the IFTTT app.
Explore more great ways to automate Notifications and Reddit