01-31-2017 09:36 AM
01-31-2017 10:42 AM
The easiest way is to is to use a Query Rule with Promoted Results, to get started see https://support.office.com/en-us/article/Understanding-query-rules-8CA2588D-9DC7-45AA-90A4-428D4D695....
@Mikael Svenson is one of the experts on this topic and he has a lot of great example on his blog, see http://www.techmikael.com/2014/03/sharepoint-search-queries-explained.html or go buy his book, it is well worth the money
01-31-2017 12:22 PM
As @Dean Gross says, use a query rule or a customized result source with XRANK to change ranking. There is not much info on the models per say, but you can look at the on-prem counter parts if you have access and try to understand it. It's not easy, as they are generated by machine learning.
I did a presentation at SPC14 with David Hollembaek which also might be useful: https://channel9.msdn.com/Events/SharePoint-Conference/2014/SPC382