Like how we normally do it, you assign Read/Write access to Modules for specific Roles.
However there is a difference between classic dashboards and NUX.
For 'classic dashboards', you cannot 'assign' a dashboard to a role in the 'Content' page, unless that role has Read or Write access to ALL the elements in that dashboard, be it module or actions.
For NUX, you need not 'assign' a Page to a role (there's no place for you to do that anyway). If a role does not have Read or Write access to any module, you'll get the following error message at Card level within NUX.
The image below shows that i (assigned to '1 Module Role') have R/W access to the module in the top Card, but i don't have access to the module in the bottom card.
Please note that the above are behaviours currently observed for NUX. As more product releases are pushed out, the above might change to improve user experience and ease of model building.
I think what you are asking here is simply how to access the new UX.
when you are connected to anaplan, you can see on the top left corner a Hamburger menu. Click on it an select Apps. This will take you to the NUX and show you the apps and pages you have access to
If you are asking how to be able to create content in the NUX, then your user needs to be a "Page Builder". Your tenant admin can assign that role in the admin console, which you can find in the same menu as mentioned above in the "Administration" section (if your org has no tenant admin please contact support)