You read and write to it exactly like a dictionary.
>>> import bsddb
>>> db = bsddb.hashopen('mydb.db')
>>> db['FirstName'] = 'Joe'
>>> db['LastName'] = 'Doe'
>>> db['Age'] = '30'
>>> db.close()
>>>
>>> db = bsddb.hashopen('mydb.db')
>>> db['FirstName']
'Joe'
However, Berkeley DB stores only pairs of key/value strings, so maybe that's not what you really need if you want to store those values for several different entries. If no other language will be using that db file, maybe you can use the shelve module to store pickled dicts. If you need it to be easy for others to use, you could serialize your form data as json. Something like this:
>>> import json
>>> import bsddb
>>> db = bsddb.hashopen('mydb.db')
>>> form = {'FirstName': 'Joe', 'LastName': 'Doe', 'Age': 30}
>>> db['joedoe'] = json.dumps(form)
>>> db.close()
>>>
>>> db = bsddb.hashopen('mydb.db')
>>> json.loads(db['joedoe'])
{'FirstName': 'Joe', 'LastName': 'Doe', 'Age': 30}
But frankly, this starts to look more and more like an anti-pattern, and unless you're absolutely restricted to using Berkeley DB for some reason, you shouldn't be doing it that way. You should be using sqlite for that.