I assume you are trying to add basic dims of the parts to the drawing. If this is not the case, stop reading here.
E.g., you have part (screw) with basic dims (diameter and length). Assign parameters to that part's familiy tab, that is add parameters diameter and length. Then you need to assign value from family tab to those parameters. You can do that by writing the following to the relations section.
diameter=ITOS(d1)
length=ITOS(d2)
where d1 and d2 are dimensions of the part model. ITOS function converts real number or integer to the string, which is needed by drawing parameter. But, to warn you, ITOS function also suppresses trailing scale numbers, so parameter diameter with dimension d1 value of 14.5 will result in value 14, not 14.5.
Parameter to bind with assembly drawing is e.g. measure. So you have to add the following to the relations section:
measure=diameter+x+length
(All of the strings in the equation above have to be String data type.)
To add that parameter to the drawing, simply type &measure into the note's text section.
I hope this does answer your question.