Deepak Gupta gave several good places to look.
You can also try looking for YouTube videos on "Draftsight" (that is SolidWorks version of a 2D Drafting package) (Draftsight is also free).
You can get generic mechanical drafting / drawing information, but depending on the package you are going to use - the methods, icons, and function names will differ.
It sounds like you looking just for 2D designing now - I would suggest Draftsight.
Later you can select your package for 3D CNC control.
Many of the CNC packages will accept different 3D formats and I would suggest you determine what 3D format you want to eventually use and focus more on that and less on the 2D.
These days, 2D drawings are easily generated by the 3D programs and are used more as a visual guide for the machinist.
The CNC programs will more efficiently use 3D than 2D.
This all depends on what your final goal is: become a machinist, design engineer,