The Sticky: Huawei S7 Useful Tweaks and Tips post has a broken link following the heading Mount SD Card in device to a connected computer through USB. The link opens to a blank page with the message "Page not found".
but to connect your internal and external cards to your computer :
you may have to install the S7 drivers from the Huawei website
1: connect your USB to the S7
2: click the " i " icon in the top right of your S7
3: click the card you want to mount
4: click mount
5: you will see a window pop up on your computer with either an option to "open for viewing" or it will open like when you double click your C: drive in windows
6: from there you can right click in the window, make new folders, delete, or move stuff from your computer to that window ( card on your S7)