Hey,
fiddled a bit with the watch today. Here are the instructions to get ADB access over USB on Windows (useful for the iOS users).

EDIT: Check this comment for an easier way: http://www.reddit.com/r/hwatch/comments/3n9ckp/how_to_get_adb_access_over_usb/cvmlqsr

First we prepare the watch (I haven't set it to English so names might be slightly off):

1. Go to Settings
2. Go to Info
3. Tap on Build Number 7 times
4. Go back, and then to Developer Settings
5. Enable ADB Debugging

Now connect the watch to the computer. It will pop up as HUAWEI WATCH in Device Manager but no driver is found. So lets fix that.

1. Download the driver from here: http://forum.xda-developers.com/google-nexus-5/development/adb-fb-apx-driver-universal-naked-t2513339
   
2. Unpack the zip and open android_winusb.inf with some text editor.
   

3. Around line 1130 add the following new lines (after the HTC ones):

   ; Huawei Watch
   %HUAWEIWATCH% = USB_Install, USB\VID_12D1&PID_1C2C
   

4. At the end of the file append (You can change the name):

   HUAWEIWATCH = "Huawei Watch Android Interface"
   

5. Save the file, open Device Manager, click on the unknown watch and install driver by selecting the directory where you edited the file.

If you are on Windows 8 and up (iirc) you need to enable test mode and disable driver integrity check. Google will help you there.

After that is done you should get ADB access. The watch will ask you to allow it, just grant access.

Proof that it works: Screenshot of fastboot mode (I didn't go any further, don't want to void my warranty ;) )

That way you can install more watch faces. There are enough tutorials around on how to do that ;)

Feel free to ask if you have questions, I hope I didn't forget anything.