See how much easier it is to read and understand without the 'tude.
What attitude? I asked some questions. Perhaps OP has good reason for naming the file with a c extension, instead of a cpp extension. Without asking for those reasons, you just want to tell OP what to do.
Perhaps OP has a reason for include Arduino.h in both places. Perhaps not. Asking offers OP an opportunity to explain, or not.
What directory do you have the files in?
the header file (MyBlink.h) is part of the project and is one of the tabs in the IDE,
If the file is a tab in the IDE, there can only be only be one directory it is stored in.