TL:DR:
Streamlabs Settings > Integrations > Tiltify > "Link" > Redirect to Tiltify log-in > Log into Tiltify > Redirect back to Streamlabs > Manage
The Details:
To connect your Streamlabs Account to your Tiltify Account, please follow these steps:
Log in to your Streamlabs account and navigate to the settings tab under "Account" in the bottom left.
Followed by "Integrations" in the Top/Middle(ish) area
OR: just click this link - https://streamlabs.com/dashboard#/settings/integrations 
On the Integrations page, click on the "Link" button next to Tiltify
Once linked, it will automatically default to your most recent published campaign. If you need to choose a different campaign, click "Manage" and choose the correct campaign you want alerts for.Once this is completed, your already existing tip alerts via Streamlabs will now work with any donation made to your active Tiltify campaign! For more information as to how to set up your Streamlabs alerts, please refer to their tutorials. For a more detailed explanation on our end, you can also refer to our integration page.