First of all HERE at the Helpindex of WT you can find how to add references in a bio.
if you add to the biography at the end of the obituary<ref>[thelinktotheobituary space obituary-Nameofsource] all other info you think is important</ref> In this case the obituary is original from a newspaper and the image of that is added to Find A Grave memorial 23283207 it was added there by M.King and copied to Ancestry by an Ancestry member.
Now a reference for this obituary can look like this: <ref>[https://www.findagrave.com/memorial/23283207 Obituary-FindAGrave] Charlevoix Courier, August 28, 1929 added by M.King 2014</ref>
I hope that was helpful!
Kind regards from The Netherlands,
OK, I should have looked at the profile before I answered.
You use <ref> tags already.
Just tag the birth info with a copy of the tag for the obituary.
The same source will be used twice but everyone can see that both pieces of info come from the same source.