I've just done something similar and this is a bit more complex than it seems so I made some notes. I may have missed something, but hopefully it will help someone.
[NB: This assumes you have HikaShop Business edition so you can configure permissions.]
I needed to allow access to the HikaShop back end to the 'dispatch team' who package and send the orders. They needed very limited access, and no opportunity to 'mess up' Joomla or Hikashop. They do need to be able to edit an order (mainly to change it from Confirmed to Shipped).
I couldn't use the Manager group for Joomla, so had to create a new group and a user in this group (parent Public).
Next, add this new group to the 'Special' level of 'Viewing Access Levels'
Next get ACL Manager (as per the posts in this thread)
In ACL Manager, you need to set for your new group the Global Configuration (first line) to being
Site, Admin, Offline (under Login) and Access (under Extension) all to green ticks (allowed)
Then go through all the ticks that have automatically been set green below (e.g. Banners, Cache Manager...) and set them to 'Denied' (unless you are not worried about your 'Dispatch team' having access to these parts of Joomla).
Then go into HikaShop -> System -> Configuration -> Access Level and set everything to Custom (Badge, Banner....) and for each you should see the group you created at the begining (e.g. 'Dispatch team') listed. For that Group I set View, Manage and Delete to empty (un-ticked) for everything apart from Dashboard (leave as View) Help (leave as All) Order (leave View and Manage depending on what you want your user to be able to do) and Report (leave on View). All others I left as they default to.
If you try logging in as your new user who is in this group, and you have not disabled affiliates, you will find they can still access the affiliates menu in HikaShop. To disable the affiliates you need to do this:
nicolas wrote: You can turn off the affiliate plugin via the plugins manager of joomla.
I might have missed something, but hopefully this helps
Steve