How do I enable Family Sharing settings for my daughter's iPhone, when I DON'T have an iPhone or Mac, only this account with which I connect online?

To set up a Family Sharing group you need an iPhone, iPad, iPod touch, or Mac. Having an Apple ID is not sufficient.

After your group is set up you could invite your daughter to the group. But if you don't have one of those devices you can't set up a family group.

See Set up Family Sharing

It can be done using one device, but it is a bit more difficult using only one device. On the device, sign into Settings/Your Name with your Apple ID and set up Family Sharing. Create the child's ID. Sign out of your ID and sign in with the child's ID. Swap Settings/Your Name  in as required.