Convert a project into codeigniter framework

I have a very straightforward system developed from another programmer with these features.
I need to convert it to codeigniter for easier maintenance or changes. You can propose a better one as well.

Users:
1. Super admin
2. Admin
3. Agent

Main features:
Agent add applicant profile
Agent add applicant details
Agent add daily debit and credit expenses
Agent add applicant daily records

Admin:
check daily total debit/credit
View total daily or customised days of applicants

Super admin:
can add/edit/delete users
can change language

Database: about 6 tables in total