has a date property
getting it in to the DB depends on what you are using.
You can (though don't do this for text input)
build a query e.g.
sqlText = "Update People Set DOB = "' + Format(calDOB.Date,"YYYYMMDD") + "' Where PeopleID = " + CStr(PeopleID);
and then exec it.
Or you can use a parameterised qurey (look that up) You'd put the code may be in an OK button, or in the Onchange event of the Calender component.
Binary stuff, e.g. Images, documents etc can be stored in Image Columns with parameterised queries, that can be google as well.
Personally, I wouldn't store binary stuff in the DB, I'd store a file name link and then store the image on the drive. Makes backing up/deploying a bit harder, but image columns can be problematic in DB,s particulary Access, which handles them very badly.
As for no choice with MDI, there's MDI syle and then there's the technology. Personally I wouldn't code my worts enemies most critical app with the latter. OK so you get menu merge and a couple of other things, but trying to keep MDI going with radically different views particulary with VB6 which by the way is turd at OO, just isn't worth the effort of not learning enough to replicate the desired functionality.
I can't help but feel you are being a bit too ambitious initially given your skill/knowledge. I hope you haven't made any promises, as I see trouble ahead.
I'd struggle to do something decent with MDI and VB6.