Open your project
(In visual studio), look to the solution explorer, that is typically on the right of your project showing all files associated with your project, you will see a orange icon that is labeled Content.mgcb.
Double click to open the Content.mgcb tool (mentioned above).
(it should open the content pipeline tool window)
Edit -> Add -> Existing item
(this will open a file browsing window)
Find your image in the browsing window and select it
(e.g. in your desktop or were ever. You may get a prompt to copy or add a reference link to the image)
Copy the item in if you are offered the option to do so. (this will place it within the content folder of your project and link it to be build or rebuilt as needed into a xnb in the projects bin folder)
Build or rebuild all the items in the tool and then click File -> Save
Close the tool.
In your project's code, we change that line to.
ship_texture = Content.Load<Texture2D>("ship");
the content pipeline initially points to the current projects content folder or bin by default.
Build your project, it should compile without error, you can also edit the image and recompile it from visual studios build or rebuild command.