... is there something I need to do before I open it in PS?
Technically, the answer is "yes", but PS does it for you automatically.
PS itself can't read RAW files. Also, RAW files can not be edited by any program. Before you can edit a RAW file it must be "processed" (some use the term "developed") in a RAW converter to generate an editable bitmap image from the camera's RAW data.
PS uses a plugin as its default RAW converter. This plugin is called Adobe Camera RAW (aka ACR). Attempting to open a RAW file in PS will cause PS to launch the ACR plugin. The file will open in ACR and you make the necessary conversion adjustments there. When finished you "Open" the image from ACR it generates an editable bitmap and passes that into the main PS application.