Official comment
This is something you can accomplish from WordPress's "Reading Settings" page.
Step 1: Log into your WordPress backend Step 2: Go to Settings > Reading Step 3: Find the "Front Page Displays.." section, and choose to have it display a static page. Step 4: Choose your hosted ONTRApage from the dropdown. Step 5: Click "Save Changes" at the bottom of that page
Here's a screenshot of what that page and it settings should look like once you've gone through the steps

