how to get dimensions? and how to work on my model?

Hi Sir,
I am student, studying Mechanical engineering. i am new to Solidworks and modeling. i have a question that from where do you get dimensions(Blueprints) of every part before modeling it on Solidworks. And my second question is that after modeling something how do you start working on it or from where to get resources and machines to make a part.
will be waiting for your reply.
thanks!!