Install Ace combat 7 in Xbox for PC.

No. You can buy it on Steam to play it on PC.

I'm playing Ori and Ace Combat 7 on XBOX ONE, and I'm also completing The Messenger DLC on PC.

The code for ACE COMBAT 6® Fires of Liberation™ will be delivered to your Xbox message center within 7-10 days of the release of ACE COMBAT™ 7: SKIES UNKNOWN.

Source:
https://www.microsoft.com/p/ace-combat-7-skies-unknown-pre-order-bundle/c3414xthf0f9

Hi there,

Thanks for reaching out to us in the forums with this question. In relation to the Ace Combat 7 pre-order bonus of Ace Combat 6, you should receive the code for the game via Xbox message on your console about 7-10 days after the expiration of the offer (02/18/2019),
so this works out to about the latter part of February when they will be received. Once you redeem the code, it will either begin to install or appear in the Ready to Install section of your Games/Apps.

ACE COMBAT™ 7: SKIES UNKNOWN Launch Edition

I hope that this information helps out!

Hey there Stephen,

Thank you for reaching out to us on the Forums. As described when viewing
Ace Combat 7, " The code for ACE COMBAT 6® Fires of Liberation™ will be delivered to your Xbox message center within 7-10 days of the release of ACE COMBAT™ 7: SKIES UNKNOWN."

I hope this helps.