I started my program and encountered an error and now would like to proceed without starting from the beginning of my program. I left off at line 6464 and need to know how to tell GRBL how to start at that line instead of the beginning of my program?
Which program are you using to send the g-code to your machine? Regardless, you should be able to edit your g-code file and delete everything between the first move (probably G0) and your line you want to resume from. Keep in mind that your bit will move in a straight line from the starting point to this line so you may want to insert a move line that raises the bit above your workpiece and moves it approximately to the x,y location you will be resuming from.
in bCNC you can turn off sections in the editor, this makes it easy to turn of everything (except the header and initial safety moves) up to the begining of the section you want to start from.