Citrix printer policy

You can only "Add" a printer to Citrix using Citrix Policies as I indicated prior.

Ideally, we leverage the printer that is already configured on the end-user device(s).  Using Citrix Receiver and Citrix Policies this printer is automatically mapped and we can choose to map the "Default Printer" only or all the printers.  

Otherwise, you can go "against the grain" and configure a Session Printers policy but it is still a Citrix Policy as I described above.
https://www.experts-exchange.com/articles/25499/Citrix-XenDesktop-7-6-Citrix-Policies-Advanced-Printing.html

Once you create a policy or modify existing policy:
In the Delivery Services Console, navigate to Policies. Select the Users tab. Enable the session printing policy in the Edit Policy.

In the policy, add the session printer using \\printserver\printersharename

The difference here being you are creating a policy for those users to map a printer on a specific print server and that Printer must already exist, be shared and configured properly.

You would then run gpupdate /force on the Citrix Servers hosting the published application associated with the users you want the policy to apply.

Also, make sure you "Enable" the policy.

So,

1.  Printer object must be configured already and shared so that users can connect to the printer directly over the network
2.  Create a new or modify existing "Citrix Policy" to create a session printer

Since you are not using the down-level client and Citrix Receiver to auto-create the printer using Universal Print Driver you will most likely have mixed results with the Session Printing so recommended to apply this to a few test users first and validate.

Also, the application and that output to a Network Printer can make a big difference in output of printing....another reason for testing first.