Sub-account are users who can access your product and services on the main account. This is typically your technical engineer or developers etc. We do not recommend creating sub-accounts for your clients if you are reselling as they will have full access to your account.
To create a sub-account, Please refer the below mentioned KB
https://5centscdn.net/help/knowledge-base/sub-accounts-for-your-engineers-or-partners-or-your-team/