When it can't find the runme.jar this means that runme.jar file is not in your current directory, so you must give the gie the whole path of the file. Just so (Example: runme.jar is in your C:\Windows directory):
java -jar "c:\Windows\runme.jar" server
When it can't find "java.exe" you have to set the PATH environment of the system to your Java Runrime Environment directory. Like so:
I think it is a good idea to give basic instructions like these. We should write the instructions as though the person reading them knows nothing about Java / the assignment. (The alternative is to assume that the examiner is an expert, but then you should not need any instructions - since instructions are required it negates that argument ).