In order to access the document store, you need to open an existing case for a client. Once you have done that, you can proceed to click on the 'document store' option located on the left-hand navigation bar.

By clicking on the 'document store' option, it will open the document store for the specific case you are working on. It is important to note that each case has its own unique document store. Therefore, if your clients have multiple cases, they will have multiple document stores, each specific to a particular case.