Storrito shares your Instagram Stories to Facebook using Instagram's own crossposting. The Story is posted to Instagram, and Instagram mirrors it to the linked Facebook Page or profile. That means the link between the two accounts has to be set up on Instagram's side first — Storrito can't create it for you.
There are three parts to it: link the accounts on Instagram, sync the account in Storrito so it picks up the link, then tick the crossposting box each time you schedule a Story.
To connect your Instagram account to your Facebook Page, you need a professional Instagram account and admin rights on the Facebook Page. If your Facebook Page belongs to a Meta Business Account in Business Manager, add the Instagram account to the same Meta Business Account before connecting them.
If you don't have a professional Instagram account, you can switch your personal account to a professional one.
You'll also need Facebook access to the Page, which is what lets you manage linked accounts.
Choose which one your Stories go to from the Instagram app:
Storrito reads the Facebook link from Instagram when you sync. Until you do this, Storrito doesn't know the link exists.
When the sync finishes, the FACEBOOK section of the account window shows the linked destination's name with its type in brackets, for example Soul.globe (PAGE). That's your confirmation that Storrito has the link.

If the section only says Facebook stories available, Storrito has no Facebook destination on file for that account. The wording sounds like a confirmation, but it's the opposite. Two different situations produce it, and they need different fixes:

Crossposting is a per-Story choice in Storrito, not a global setting. There's nothing to switch on once and forget about — you decide each time you schedule.

Storrito remembers your choice, so the box is usually already ticked the next time.
On the Schedule page you can tell at a glance which Stories are crossposting. Each card stacks its destination icons in the top left corner of the thumbnail, and a crossposting Story gets a Facebook icon underneath the Instagram one. Hover it and the tooltip reads Cross-post to Facebook. The card also shows its status, such as Scheduled, in the top right.

The row doesn't render at all when Storrito has no Facebook link on file for that account, and the scheduling page doesn't explain why. Work through Part 2 above: sync, check what the FACEBOOK section says, and reopen the scheduling page.
If syncing doesn't bring the Page in, see Facebook Crossposting Troubleshooting.
This applies to Stories only. The Recommend on Facebook checkbox in the Instagram Reel options card is a different feature. It lets Instagram recommend your Reel to people on Facebook; it does not post the Reel to your Page.
Only question stickers stay interactive on Facebook. Link, poll, music, and quiz stickers appear as static images once the Story is mirrored across. See How To Share Your Stories On Facebook.
To stop crossposting for a single Story, untick Share to Facebook on the scheduling page.
To unlink the accounts entirely: