Hello Community!!!
I have a Question:
I have used the avast Home Edition for the last Year and will use it this year again. I have the Key but what I do now??? Please help me.
mfg Baalik
Ps: Sorry, my English is not great.
Welcome to the forums, Baalik. 
Right click the “a” ball on the task bar > click About avast! > in opening window, click License Key button > use “copy and paste” method to put key in box making sure there are no extra blank spaces > click OK
The key is valid for 14 months only. Go to the SSL page version and register from there: https://secure.avast.com/scripts/register.php?lang=ENG
See the tutorial: http://www.avast.com/files/tutorials/insert_key.htm