If you are the first person in your organisation to respond to a String3 question sent by a customer, you will automatically become the admin of your organisation's account.
If your customers send questions to other people in your organisation they will not be able to respond unless you have added them into your account.
To do this, navigate to the dashboard on String3 and on the right hand side you will see an option saying "Users" underneath the name of your organisation. Click this.
You can then add colleagues to your organisation's String3 account. Select the "Invite a member" button and add in their names and emails. They will then be sent an invite to join String3. From there, they can respond to customers' questions.