How to use iCloud to send someone a picture?

If they have access to your iCloud account, i.e. they know your login credentials, ALL you data is theirs to view and use. All that's in iCloud Drive that is.

iCloud Drive is not a file sharing service, it's an interactive service for users. It allows your data to be shared on YOUR various devices.

You can do this: Share iCloud+ with your family - Apple Support

In Photos, you can create a Shared Album

If they have iCloud Accounts: Share files and folders in iCloud Drive on iCloud.com - Apple Support

If the file is too large for email, you can send it via Mail Drop.

The picture in question is already in you iCloud >> Photo Library - YES ?

Choose the method from " Mail " to " Messages " or other available methods

refer to below

Frank - No I can not see your Photos in your iCloud account

The partial picture in my posting, if you look closely, is not your photo but Mine.

EDITED

Sorry Frank but " Why you can see it in my cloud?" kind of implies otherwise.

" One Drive " from Microsoft - that is off the Map for me.

See https://support.google.com/drive/answer/2494822?hl=en&co=GENIE.Platform=Desktop

Mail Drop is free.

I linked to it in my first post.