You need essentially 2 things to start a bank:
Borrowers - People that want to borrow money from you and are willing to pay you interest on the loan. You need to be able to trust that these people will pay, and/or you need a way to enforce payment.
Money - Either your own money or people willing to loan you money at an interest rate that is (at least slightly) lower than what you can extract from your borrowers.
Also helpful:
A gathering place for borrowers and lenders, such as a discord channel.
A storage location (nation or alliance bank) that is reasonably safe from raiding where you can temporarily stash large sums of cash.
A trustworthy staff to help you with raising capital, collecting interest, and paying interest.
To make your bank successful will require a trustworthy reputation and a lot of work.