[Jcoop]

I'm not sure I fully understand your question. You want to assign Bar 1 Beat 1 to a specific timecode? If this is the case, just spot your cursor to that timecode position, press command+I and type in bar 1 beat 1.

This will also snap the default tempo marker to that position and you can set the tempo by double clicking on the red marker on the tempo lane. You can apply subsequent tempo change at a new selection point with the + symbol on the tempo lane.