The use of Command Line Arguments is quite simple; it's merely typing a few words and/or numbers.
You can find instructions here: https://wiki.guildwars2.com/wiki/Command_line_arguments
Use the Command Line Argument posted in several of the other threads concerning this issue.
Press WindowsKey+R to open the run dialog, then enter:
C:\Program Files\Guild Wars 2\Gw2-64.exe -assetsrv 188.8.131.52
This is assuming a default 64-bit install of GW2. If it's somewhere else, you'll need to find out where by right clicking your GW2 shortcut and selecting properties or open file location. If you selected properties, it should have opened a window with a shortcut tab selected - see the target box for the full path (this is where you'd normally add your command line options). If you selected open file location, it would have opened the folder where it's located. Modify the above with your own path.
Click your shortcut icon for GW2.
A little window should appear with tabs at the top. One named 'Shortcut'. (Should open to that, if not click the 'Shortcut' tab.)
In the 'Shortcut' tab window is a field called 'Target'. This shows the path (or Command Line) for launching GW2.
Whatever it says, place your cursor at the end of what's written there. Click 'Space' on your keyboard, then type: -assetsrv 184.108.40.206. Then click 'Enter'. Close the window, and double-click your icon to launch GW2.
Once you've downloaded the files, remove that (Command Line) Argument you typed in.
Glad it's working for you!