1.how to draw free body diagrams and how to resolve it and write equations for those?

Steps for drawing a force diagram:

1. Identify the object you will draw a diagram for.  (If there are multiple objects of interest, you will need to draw multiple diagrams.)
2. Identify all the forces acting directly on the object and the object exerting them.  With the exception of gravity and certain other forces rarely used in first semester physics (magnetism, electric force), the two objects will be in direct contact.  Do not include forces by an object acting through another object--only include the force due to the intermediate object.
3. Draw a dot to represent the object of interest.
4. Draw a vector to represent each force.  Draw it in the direction the force is being exerted, and label it by (a) the type of force, (b) the object exerting the force, and (c) the object receiving the force (which will be you object of interest).  It will have the form F(type)_{exerting object -> object of interest}
5. If the object is stationary or is moving at a constant velocity, the vectors should graphically add up to zero.  If the object is accelerating, the sum of the vectors should produce a vector in the same direction as the acceleration.