Choose "Results to Text", then copy/paste the results into a new window.

declare @OldOwner varchar(100), @NewOwner varchar(100)

set @OldOwner = 'oldowner'

set @NewOwner = 'dbo'

select 'sp_changeobjectowner ''[' + table_schema + '].[' + table_name + ']'', ''' + @NewOwner + '''

go'

from information_schema.tables where Table_schema = @OldOwner

You can skip the variables and hardcode the owner names in the script.