Why do you think you need to do that? The project doesn't call for the client and server to be merged and given the project definition ("...by use of a client/server...") it would seem you need a separate client and server.
But anyway, it's easy enough if you understand the code. Just copy the functions you want from the client to the server (or vice versa) then modify any functions that need modifying in order to call those new functions in the right place. Obviously you can't have duplicate functions, so for instance if there are two foo() functions then you'll need to work out (a) if they are different functions with the same name, in which case just rename the function; (b) if they are identical, in which case delete one, or (c) if they implement similar functionality but slightly differently, in which case you will need to merge the logic. In any event you'll need to understand *fully* the existing code.
My suggestions are (a) that you focus on what the project asks for without adding in your own extra tasks (maybe do them later for extra bonus marks, but if you just do the project on its own, well, you should get 10/10); (b) take an overview of the project requirements but when it comes to implementation make sure you write just a few lines at a time before compiling it and making sure it works correctly.