Translation of Kennzahl

I learned Russian during 8 years in highschool, but since I left school 6 years ago, I have forgotten most of it and did not have opportunity to speak or practice in any way. That's why I am on Vocabulix.
Maybe we would need to say install our dictionary as a software? But I would say instead of install, use our dictionary as a software. So bottom line. If I use the singular form for newsletters and websites, I am on the safe side for both?
Now I am learning by other means, such as reading and writing. I can not begin with conjugation training because I lack the basic knowledge. How are you learning at this site and which is your best lesson?