Step 1: Open User roles under Settings tab from the navbar.
A list of all users show up on the right. Each with two buttons.. The left option indicates Edit and the right one indicates delete.
Step 2: Choose the edit button to manage roles for that particular user.
Step 3: Edit permissions.
From the list, you can edit user permissions for this user. If this is disabled, then that just means you are not permitted to change user permissions.
Additionally you can give a user ‘admin’ access which just ticks all permissions from the User Access list.