Do you own the root domain omnitech-security.fr if so you may need to create an internal host file entry to test, or an internal DNS entry for the local server.
When ready to deploy if this will be publically accessible then you will need to set a public DNS record for the URL with your domain registar or whoever public DNS record is kept.
If you’ve never hosted web before, should probably figure out the basics first before doing something like hosting an important service like Bitwarden. It’s probably pretty possible but seems like a PITA in addition to any insecurity from inexperience.