To apply anew...you just apply, as though it were the first time.
In making the application you'll be asked if you've ever previously been refused a UK visa. You should answer truthfully. UKVI will know about your previous application and refusal and ban: if you don't reveal them in the new application, UKVI will have you (again) for lying on the application; you'll be denied (again), and, perhaps, banned permanently. You should reveal your previous history, and understand that whatever your passport "agent" did in the past is your own responsibility because you were the applicant. That is, you cannot avoid responsibility by attempting to blame the "agent."
A new application from you will be scrutinized very carefully. It is likely that your previous refusal and ban will count very heavily against you, and significantly reduce the chances that this time you will obtain a visa.
Because of your prior refusal and ban, you should consider hiring a UK solicitor (i.e., a qualified lawyer located in the UK) to prepare the application for you. Do not use a local "agent."
Hiring a solicitor in the UK will be expensive. All of us here would agree that hiring a UK solicitor will increase your chances of success. Even if you do hire a UK solicitor, however, there can be no guarantee that your new application will be successful.