Here is William's second marriage to Eleanor Newman:
"New York, County Marriages, 1847-1848; 1908-1936," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:QKJM-WMDR : 18 March 2019), William A Lockhart, 7 Jul 1928, Monroe, New York, United States; citing ref. ID 6739, county clerk offices from various counties, New York; FHL microfilm 831,371.
To add his second (and third) wives, just click "add/remove spouse" at the bottom of the "Spouses" section on the right hand side of the profile when in the "Edit" tab. You will then be able to enter all the relevant details.