Hello!
First of all you have to enable the developer options on your watch with these steps
1. Open the Settings menu on the watch.
2. Scroll to the bottom of the menu. If no Developer Options item is provided, tap About.
3. Tap the build number 7 times.
4. From the Settings menu, tap the Developer Options item.
5. Enable ADB debugging.
After that you'll have to prepare the apk's you want to sideload by extracting them from your phone by using an app like
apk extractor or any other means that you prefer. Open one by one the apk's from your computer with winrar and extract the wear apk located usualy in the "raw" or "assets" folders in the same folder that you have the platform tools. You may have to rename them because they all have the same or similar names. (make sure you don't use spaces or other special characters)
Then you connect your watch with the usb cable to your computer and accept the adb message that you'll see, if you don't see any message you'll propably see it in the next step.
Open a command prompt window on the folder that contains the platform tools and type "adb devices" just to make sure that your watch is connected.
After that you start sideloading the apk's by typing "adb install myapk.apk". (replace "myapk.apk" with the names of your apk's)
Because this may be a bit boring to type one by one every apk you need to sideload, an easier way to do it is by creating a txt document in the same folder as your platform tools and start writing down the commands in seperate lines, like this:
adb install myapk1.apk
adb install myapk2.apk
adb install myapk3.apk
......
......
close it and save it. rename it to something like "sideload.bat" and when you're ready just double click it and just wait to finish. Make sure you change the extension of the filename from ".txt" to ".bat"