Clarity

Good morning.  Can I make a field read only, but still be able to enter information into it before hand?  Meaning, we have an idea and we want to turn it into a project.  In the form that comes up there is a date field called "planned start date".  When converting the project I want to be able to put in the data from the project charter, but when the information is saved, I'd like for the field to be read only so nobody can change it.  Is this possible?  

"Enter once" is the thing you want I think

([Fields] property rather than the attribute property)

(field is enterable whilst it is blank, but readonly once data is present)

You can either enter once feature (as mentioned above by David) or lock the attributes when you have the data (thru process). The locking option will be good if you are planning to have a workflow to review/change the field you mentioned.  

Thank you.  Are there instructions on how to complete these steps?

It is difficult to explain the steps through a case comment. If you have worked with processes earlier, it should not be much problem for you.

Else it is better that you go through the documentation:

CA PPM 15.4 - Configure Processes

Hope that helps.