It's vital that all your team members have access to the tools needed to complete their job. QuickBooks Online is a great tool able to help you access your books from anywhere with an internet connection. I can provide some information about adding users.
In order to add a user to your QuickBooks, you can follow the steps outlined in this article. There's also a video tutorial in the link as well to help guide you.
If you have any other questions, feel free to reach out here.