clicked the button to download my active key, windows can not read it. what should i do?
Welcome to the forum. 
Have you already install Avast ?
Once Avast is installed, Avast will read that file.
i had to uninstall due to the fact that the update made my computer not receive any wifi signal, so it is now not under the list of programs that will read the file
And how do you think to use a key without the application ?
Install avast and use the key.