After that course the new internal auditor can start performing internal audits. Starting in a known environment and with known auditees helps a lot in the first audits. Smaller audits can be done, frequent audits can be done, several techniques can be tested, and helps build trust in own capabilities as time and stress manager.
After several internal audits you can start trying a new environment, performing internal audits as an external auditor. That will test your ability to audit with different people, with different operations and with different cultures.
After that course you can contact several certification bodies and give them your CV stressing your experience and qualifications.
Complement your training with reading whatever you can find about preparing, performing and reporting an audit. I find it useful to discover new tools to use during an audit and learn what other professionals think. You can start with these articles and book: