If you purchased a brand new Lenovo computer directly from Lenovo, Windows was activated at Lenovo's factory, so there isn't anything that you need to do to activate.
If you purchased your computer under other circumstances, what you need to do in order to activate Windows depends on how you purchased your computer. I do not like to guess or make presumptions. Tell us how you acquired your computer, and how you acquired Windows, if Windows was separately purchased, and someone will tell you exactly what you need to do.