I have been asked by my manager in a new company to document processes and visit our other sites. ie. capturing customer details etc.

I have asked the usual - who is the audience so I can decide if I use BPMN or EPC etc.

He has requested that I document "where" the data is stored. I have done class models once before which shows what attributes are stored  - but not "where" so stating what database etc. Is there a way to include that in Class models or is there a specific diagram notiation to use?

I know EPC say which system is used to capture the details or for each activity but this does not related to "where" it is stored.

Any help would be greatly appreciated as I have googled but I am struggling on what to search for, and I am a single BA in a new company.

Don't a head of yourself by focusing on tools. Tools are of little use if you do not know the context in which to use them.  There is little sense in documenting a current process with out the intent to make improvements to it.  It is important to follow this basic process analysis process:

1. Why are you analysing this process?
2. What kind of process is it: highly automated, automated with add-hoc exceptions, partially automated with planned exceptions, case by case?
3. Identify the Stakeholders of a Business Process
4. Document the Process Goals and Identify Metrics for Improvement
5. Model the Current Process just enough to understand its issues
6. Determine Causes of Problems with the Process
7. Determine Process Improvement Options
8. Make the Business Case for Process Improvement and present your findings - remember to make them SMART
9. Provide a Plan for the New Process Implementation

You do not have to be (nor shoo.d you really) an expert in the process you are analsying but you should be an expert in the process of analysis

Perry McLeod