I am pushed for time so would ask that you learn how to create an arduino lib in the arduino.cc/forum

Once you understand how to create an arduino lib in the right way it will be automatically recognized in both the arduino ide and vs

If you do manage to create one it will appear on the "project>add arduino library>user" menu which can be clicked to insert into the current sketch. Once you understand how libs work you would also be able to add the lib manually to the sketch


Once you have added the lib to the project the menu item "Project>show all arduino files" will bring the library sources into your test sketch.

Remember that your actual sketch "will use" the library and will "not be" the library

edit: this might help...

create a folder called MyFirstLib under c:\my documents\arduino\libraries
add a .h called MyFirstLib.h
if vs is already open click "Project>add arduino library>refresh"
if not already open then open a sketch
then click "Project>add arduino library>use>MyFirstlib"
then click "Project Show all Arduino files"

you can add #includes for libs manually to the main pde/ino file but the libs must reside under the libraries folder mentioned above. adding #includes manually will not be recognized by vs until you save the pde/ino

there are no paths to set because you only have the option of a couple of known auto discoverable locations