HiTask Premium or Free account supports only assignment of tasks, but not sharing.To share items between team members you need HiTask Business account.Don't worry - if you upgrade your Premium account, everything you paid for it will be credited toward the Business account.HiTask Business account have 5 user licenses initially that you can assign to your team members. You can add more user licenses at any time.
Please go to
Signup page to upgrade your account.