just sign up with your twitter or facebook account here:
https://www.thunderclap.it/projects/66402-are-you-still-waiting
Also @jaraumoses wrote a nice tutorial: https://steemit.com/promo-steem/@jaraumoses/how-to-sign-up-for-the-steemit-twitter-thunderclap-promo-steem-team-lets-make-stemit-trend-on-twitter-2moro-we-go
If you need more information, please be specific in what you need to know, I'm available on Discord.
I do not ge it neither, this is about sharing what? Every user will share one post of theirselve on a tweet or will share the link of steemit or what? what do i have to share on that tweet?
You just sign up with thunderclap and they do the rest.
They will ask to post this one tweet from your account (and everyone else's) at the same time and so Steemit will be trending for sure tomorrow!