Apps can be added to BlueStacks App Player by clicking on the BlueStacks Channels icon. There, dozens of other Android apps are listed and can be downloaded with your Web browser by clicking the app icon.
BlueStacks also offers Cloud Connect, which allows you to transfer apps from an Android phone to a PC or tablet. This is done by first installing BlueStacks on your Android phone and then uploading apps to the cloud version of BlueStacks Cloud Connect for download on your PC or tablet. While not yet available with the alpha version, the final product will let you download apps from the Android Store.