As a Wix Website Designer, I find that clients often want to be able to give their staff the ability to edit the website, but they don't want to give them the keys to the entire account (such as the ability to view edit payment info, delete or duplicate the website or view other Wix websites in the same account.)
The Wix platform has a simple solution for this, all you need to do is give people editing access. See my screenshots below, you can do this under the Roles & Permissions area in the Wix account dashboard here: www.wix.com/my-account
Here you can assign anyone to be a Contributor to the website, and you can also control whether they can make edits and publish the site (or you can also just let them make changes without the ability to publish live to the website, so that you can review the changes first before going live).
You can also give them "Back Office Manager" permissions which would allow them to access the settings and apps (such as manage contacts) but not have the ability to make edits to the website.