I believe you want to make changes in Cimplicity screen files (.cim) of your unit. To do this, you need to open the .cim file in edit mode. This will start the program "CimeEdit" to allow you to make the required changes. CimeEdit user manual gives you the required guidance.
Editing Cimplicity displays, while not an easy task in itself, is only one step in the process and the process is not documented anywhere *and* it can vary with the version of Cimplicity.
Any data or value you want to display must be in the Cimplicity project.
To retrieve data and values from the Mark VI, they must be present in one of the EGD Exchanges in the Mark VI.
So, if the desired data or value(s) is or are not present in an EGD Exchange it must be added to an appropriate EGD Exchange. You might try the Toolbox Help file for this information; it's worth a try because it's not documented anywhere else. This 'step' in itself requires several steps, and can vary depending on the version of Toolbox and the micropocessor card installed in the Mark VI. The change(s) must be downloaded to the Mark VI, and if there are multi-unit HMIs on site, there are a lot of updates which must be done.
If the data or value(s) exist in the EGD Exchange(s) but are not in the Cimplicity Point Database, they must be added to the Point Database. This also varies depending on the version of Cimplicity.
One can't copy displays between HMIs without a lot of extra effort and work. So, one must create/edit the display(s) on each HMI to make them all match.
Without a clear understanding of the steps involved, and, again, they can vary depending on the versions of software and hardware. And, if the site is a multi-unit site with other Mark VIs and exciters on the UDH, it can get very complicated very quickly.
Sounds like a job for someone with the ability to get help from GE, if needed. Because unless you make good backups before you start (you should *already* have good backups; you do, don't you?) *and* you have created a checklist of all the steps required and know what to do and when, you can create a very big mess. It's been done before and will likely be done again; most times the hard drive "dies" mysteriously, at least that's the complaint when there's no backups.
Seriously, you should really contact your original equipment supplier (GE or a packager). PLC programmers with Cimplicity experience usually just go crazy trying to understand the interface with the Mark VI and usually don't understand the Mark VI or Toolbox.
Do yourself a favor; leave this to someone with experience or a way to get help from GE if needed.