Hi Peter, when your record is open, scroll down to the bottom of the page and you will see Citation for this record. Highlight the link and copy it, then go to the profile that you are sourcing on Wikitree and paste the link Under the sources heading.
when you are done researching then you can write up the Biograpy: eg. John was born on 12 march 1880.<ref>...................</ref> in London, England, United Kingdom.
Highlight the link in your sources and paste it where the .......are. don't use the dots I just put them in to show you where to paste the link.
now you can delete that link from your Sources.
it will show there under your Source heading when you save and return to tree view.