Hi Tia,
Can you specify what you mean by “they can’t seem to access MyStyle correctly”?
What do you want them to do – design something on the front end, or edit settings for products on the back end?
If Front end… the default in WordPress for a user signing up on the site would be Subscriber. When they log in, they would still land in the wordpress dashboard by default, you have to set up WordPress settings or use plugins to make it so that a logged in user lands on the front end and never goes into the admin dashboard. This is outside of the scope of what MyStyle does as a plugin, and is handled entirely in WordPress. Anyone can access the saved designs by going to the link in their saved design email, or going to {yourwebsite.com}/designs/ and finding it in the gallery if it was a public design. If it was a private design, you have to log in as the author to view it (Admins can see private designs as well).
Have you tried going to your public /designs/ gallery URL?
If Back end… You can use a User Role Manager plugin for WordPress to make custom admin user roles that have access to certain portions of the admin. That is outside the scope of the customizable product features that MyStyle enables. If you have a managed license, your account manager can probably open a ticket for this to be set up for you. If you have the Design Manager installed, you can set up a new role like Admin that only has access to the Design Manager, but that’s more to do with custom permissions and roles in wordpress than MyStyle, you can manage any plugin page’s access that way.
If you can describe the user experience you want to happen, I can point you in the right direction of some plugins that might help.