How do I insert an image to my post, and to my signature?

There is a great forum where that question is often brought up and answered.

Go to the Forum Technical Assistance forum, down in the Feedback, Help, and Testing section.  First look over existing threads, and you may find good help without even having to ask the question.

I use imgur for photo's and method is the same for posts and it is for your signature.  Check out this link

http://cs.finescale.com/fsm/feedback_help_and_testing/f/22/t/186686.aspx

I suggest you "google" this question, adding "finescale" as well.

there are literally dozens of instances of ask-answer.

Bill