Hi Amit,
You need to define, the Screen layout for the BP and GL Line Items in Config.
IMG-->Financial Accounting-->Contract Accounts Receivable and Payable-->Basic Functions-->Postings and Documents-->Document-->Screen Preparations-->
1.Define Screen Variant for List Entry of Business Partner Items
2.Define Screen Variant for List Entry of General Ledger Items
Once you have defined it, in FPE1, you need to give the line layout and then you will be able to post the FPE1 entry
You can set the parameter IDs 802TC and 803TC at the User role profile,so it gets set by default, once the User executes FPE1
Hope it helps.
Thanks,
Amlan