Yes. This can be done by selecting :Team: via the account drawer in the bottom left-hand corner of the main dashboard. Simply input their Name and Email address and select :Add Member:.
If your account has no additional team seats available: You will have to add a seat via :Bill Info: in the bottom left-hand drawer in the main dashboard. Once here you will need to add the seat by updating your plan. Additional seats cost $5 per member, monthly. Increase or decrease your team size as needed.