My Facebook pixel required to verify my domain to use Facebook pixel. I need help to know how to do this process

On our side? Isn't this something you need to do on Facebook? Don't they have instructions?

https://developers.facebook.com/docs/sharing/domain-verification

and
https://www.facebook.com/business/help/286768115176155?id=199156230960298

"Who is Domain Verification for?

Domain Verification is the best way to handle ownership if:

• You have the ability to upload HTML files to the web root directory or the ability to edit DNS TXT records"

I don't think you're going to be able to use itch.io for that, you need to purchase a domain and get webhosting, I recommend GoDaddy because for fresh accounts the first year is $1 (if they still do it) then for hosting you can get a free one at 000webhost, once you have both change the nameservers on the domain to the ones you have from 000webhost.

Then you can either upload the HTML file or add a TXT record on your DNS (probably easier to just do the HTML file) with an FTP software, Filezilla should do it just fine.

i do not recommend what facebook is offering they are selling data you could have done with another program. Plus many people block cookies or have extensions to block cookie. All you are doing  is giving facebook free data on you.

Thanks to all of you for good suggestions. I think I should avoid Facebook business for my itch.io account