Just check out this link - it gives all the address details you need :

http://www.pmb.co.nz/images/lcd_dwg_1.pdf

Hopefully you should be able to write to the second line. Tip : Kindly note that when a character is written, the auto increment of the display ram happens only within the particular line. It does not roll over to the second line automatically - you need to set the address for the second line forcefully.

Raghu