Help about commands of 16x4 LCD - JHD164A
I think it's 10dddddddd where dddddddd are the address bits (RW is low)  

So to set cursor to start of line 2 it's probably something like 1000100000 (first two bits are RS and R/W)

Here is the KS0066 controller datasheet (I believe that LCD uses) so you can check yourself.

EDIT - most 4 line LCD displays use two controller ICs IIRC, and the addressing is usually:

Line 1 = 0x00
Line 2 = 0x40
Line 3 = 0x10
Line 4 = 0x50