Go to your Parse on Buddy app’s dashboard under App Settings -> General -> App Management. Click on the ‘Set external URL’ button, and copy/paste your MongoDB connection string.
Update your client apps (see here for details), test, and publish to the app stores.
Wait until your users have upgraded to the new version that uses Parse on Buddy (if your app was already in production).
Finalize migration by going back to the dashboard and clicking the ‘Migrate data’ button. During this migration, we will copy the contents of your MongoDB to ours, and then immediately switch over to this new copy. At that point, your old self-hosted instance will not be used by Parse on Buddy anymore, and you can safely archive and/or delete it.
Ensure your MongoDB can be connected to over the internet, with authentication. A good way to do that is to download an open-source MongoDB viewing tool, like http://www.mongoclient.com/. Make sure the user name and password are in the connection string, for more details see here.
Since this is a database copy, there will be a hiccup while we copy/switch over. The downtime depends on the size of your database, and is typically nearly instantaneous, but may be anywhere from a few seconds to upwards of a few minutes, depending on the amount of data to be copied. We recommend finializing at a time that you determine will least impact your users.