I know this is an old question but I want to answer this as it is still relevant today.
When the server has the "Windows Search" feature installed through the server manager it will be capable of indexing files that it is sharing with the domain/network(in other words stored on its hard drives) and allow a windows 10 computer to utilize the index for search purposes. In the control panel of the server you can access the "Indexing Options" and configure the indexing locations (on the server hard drive that will be shared over the network), the indexing types (i.e. .PDF, .docx ...), content indexed(file name or file name and file contents), and other settings. It is a very strait forward implementation and I would agree that there is a lack of good documentation on this subject.
To answer your question, if you have correctly setup the search on the server then you don't need to do anything on the client to use the servers index assuming that the client is a standard installation and has access to the server shared folder.
- Install "Windows Search Service" by going to Server Manager -> Manage -> Add Roles and Features -> Select "Windows Search Service" on the features page -> install
- Create a shared folder at "C:\\Shared Folders\Company Files" with the required permissions to access the folder from a client computer
- Open "Indexing Options" and click modify to add the "C:\\Shared Folders\" to the indexing list and click advanced and select "Index Properties and File Contents" for searching inside the documents
- To access this folder over the network from a client computer go to "\\Server\Company Files" and the client computer will utilize the servers index to complete the search. You can monitor the progress of the index in the servers "Indexing Options". Note that you should not have the options "Advanced options"-> "File Content" selected on the client computer. Also it will take some time to complete the indexing and there is a way to remove the limit on the indexer for faster indexing of files.
ISSUE: there is a condition on windows server 2012 r2 essentials that I have not found the resolution to in which the client computer will not use the index on the server. The condition is if you are using the "Shared Folders" in the address like "//fileserver/Shared Folders/Company" instead of "//fileserver/Company" which will utilize the index on the server. I have created a new question to try to resolve this here