Freddy,, hi, have you explored the Chart of Accounts to find the account register? When you've located the register, open it to find the transactions. Go to the bottom of the register to find the options for data entry in that register. Depending on which register you're talking about the options will vary. If this is a liability that has a sub-ledger, like Accounts Payable, you won't be able to edit the register directly. Same goes for Payroll and Sales Taxes. But other registers for miscellaneous liabilities can be edited directly in the register.
Forms live in registers. If you enter something in a register and go back to edit it you will find that the form has been generated by your entry to the register. Often there will be a selection of what type of form you'd like to use on the line you enter data into on the register.
Hope that helps. If you provide more information about what specifically you are attempting to accomplish I would be happy to provide you with more guidance.