Read point

so if my x,y,z origin is lets say Datum A bore but my read point is datum B bore.

1.I have to manually put the centre point coordinates of datum B for read point? and then do alignment x,y,z origin and offset x,y,z ?

2.Also if i don't have a part. I am just making a offline program can i still give a read point? How would that work? 

3. i made this program offline. And when i got the part i try to give it a read point. Datum A as cad orgin and datum B as a read point. Aligned the read point and offset the x,y,z so that the origin is back to datum A. It started giving machine out of parameter error. 

4. Read point should always show x,y,z zero? what if when i click read point and the values it shows is like 313.580, 441.031,311.054 (just an example) why does it do that?

Thats a lot of stuff in one post. 

Have your part origin set in the "correct" location.
Add your read point in the proper theoretical location from your origin point.
Establish the readpoint and translate XYZ to the point, then translate it back to the "correct" origin location.
Generally, its always in a hole, so grab a circle and set the origin to the circle and then translate it back. 
Normally there is something close by in Z so grab a point and set Z to the point, and translate it back. 
(there is a theme here you can see) 

Here is an example I used the other day. (that part is the size of a Volkswagen) Good tooling helped us get the hotdog down the hallway!  
 

thankyou