Devs said on the  2nd of December 2020 this vlog if I remember correctly.

U can get them free only from containers : ( 
my friend opened a cont just once and he got Fire immunity from that tho : O 

This’d give you all the information you need.  To equip it you need to go the garage and equip it https://en.tankiwiki.com/Augments
And it’d be better if you ask questions in this topic https://en.tankiforum.com/forum/375-questions-answers/

They said it would take another month or so due to the large number of layers who entered. So most probably will be like mid July or beginning.