Welcome to the forum Tanya. There's a lot of great information here to help you reach your goals. To answer your specific questions, push-ups are a great exercise for you to start with. Here's a link to and article by Craig Ballantyne on how to progress with push-ups.
How To Do Pushups And Build Beautiful Arms
Craig also has a good blog post and video on lunging progressions. Split squats or lunges are a great starting exercise for your hips and legs.
Turbulence Training: Lunges vs. Split Squats
While push-ups and lunges are a great place to start, a good program will be made up of more than just two exercises. Craig has lots of good information. He has a newsletter you can sign up for if you want to.
There's also a new book due out this month called
The New Rules of Lifting for Women by Lou Schuler, Cassandra Forsythe, and Alwyn Cosgrove. We are all excited about this new book and I encourage you to get it. You'll learn exactly what you need to know to reach your goals.