Hello Jessica,
There are a few ways to do this in EPPI-Reviewer but the best way to proceed will depend on what your client requires (and how they wish to use the data).
You could generate a coding report by selecting the items you want to export and clicking on the 'Get coding reports...' icon. In the 'coding reports' window that will appear select the codeset (I'm assuming it will be your 'screen on full report' codeset) and click 'Get reports'. This will generate a report in the 'Report viewer' that will contain the citation and the selected code(s). If you then save the report as an html file you can then open it in excel (and then save it as an excel file).
Another way to do this is to create a configurable report (in the 'Reports' tab) that is set up to display the selected codes from the chosen codeset. You can tell the report to include the title,year, abstract and short title (which is the author and year) along with coding that you have requested. This will create a table in the 'Report viewer' that you can then save as an html file (and thus create an excel file).
If your client is able to work with JSON files you can export your citations and their coding using the 'coding report' funtion (as described earlier). In the 'coding reports' window there is an option to save your data as a JSON file. This file will contain all of your citation and coding data.
Finally, if you are looking to create an online database of your systematic review, EPPI-Reviewer has a web database utility that many people use to display their data. If you would like to know more about that please let me know.
Best regards,
Jeff