I was wondering how to add more fields on transactions like the memo field.Is it possible to do so.. How can I do that?
If you need to store some information attached to any account you can use
ManageData operation to store key/value pairs, more here https://www.stellar.org/developers/guides/concepts/list-of-operations.html#manage-data
Please note that ManageData operation will store information for the account, which can be edited/deleted, and not attached to a particular transaction. Where as Memo field is attached unique to every transaction.
There is actually a memo field in stellar that you can add in a transaction, check out this link