dipu,
get into 7.13.1 Pending Invoice Maintenance enter your SO number.
In the last frame, after tax data frame, u have fields
Ready to Invoice: No AND Invoiced: No.
Check these fields. make "Ready to Invoice : yes" and then print using 7.13.3 Invoice Print, update flag as yes, INVOICE number is generated.
Copy that number and then post it using 7.13.4 Invoice Post. A GL transaction will get generated.
HTH
Shiva