First of all, if your Stratux is working OK and you are receiving towers and seeing weather and traffic, there is no reason to update anything. However, if you want to upgrade to the latest software or need to upgrade for some reason, then...
Go to http://updates.stratux.me/builds/ on your computer using your internet browser. Click on the latest file to download the latest version of the Stratux software. Remember where your computer downloads it to so you can find it in the following steps.
Next, connect your computer to your Stratux via WIFI. Again, using your browser, type on the address line 192.168.10.1 and press enter. This will open up the Stratux application on your computer.
There, in the top left corner, click on Menu, then Settings.
Look near the bottom of the screen on the right side for "Click to select System Update file" and click on it. Then, click Browse and find the file you downloaded previously. At this point, follow prompts to install that file on your Stratux.
You can do all of this from your computer or tablet.
And yes, this whole Stratux thing is not customer friendly, but it was not really intended to be. It is not really a commercial product. It is an ADS-B device and software developed by several guys, more or less as a "hobby," trying to come up with a low cost alternative to commercially available devices that sell for almost $1,000.