As George Fulton says in the comments, if Phebe is William Wilcox Warren's mother just head over to the Edit tab of his profile here, click the "add mother" link, then add Phebe's WikiTree ID which is Briscoe-784.
"Pedigree Resource File," database, FamilySearch(https://familysearch.org/ark:/61903/2:2:SGJG-XK2 : accessed 7 July 2018), entry for Harriet Phoebe (2nd Wife) /Briscoe/; file (2:2:2:MMS9-QX9), submitted 4 May 2011.
Could not find any good sources for Harriet Phoebe Briscoe but the above user submitted tree shows Phoebe, first name Harriet, as William Wilcox Warren's mother. I have linked Phoebe as WWW's mother as Karen suggested.