I created a new module and am unable to create a related list for it.

I created a new module and am unable to create a related list for it.

Because of the nature of my business I needed to change the default "accounts" Tab into my Clients tab so I needed to create a new module for my client's accounts ( I am a financial advisor and my clients many times have more than 1 account). I am wanting to be able to see a list of the accounts when I open a client record but am unable to do so. HELP!