Before the steps on how to achieve this, to assign a team member to a client, please make sure that the team member is added to your account first and has an "Editor" role.

To check if you have this specific team member on your team. You can do that by going to your account settings and choosing the "Manage team" option. If the member is not on your team yet, you can add them by pressing on the "Invite new user". For more detailed instructions, please check the following article.
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After these steps, you can assign the folders in the "Manage Team" section by clicking on "Change Role" section.

Or by returning to your home screen and clicking on the three dots of the chosen folder, you will find the option to share the folder. In the pop-up window, choose the member to invite and click on "Send an invite".
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