How I get Kirin mount?

How I can unlock "A Legend for a Legend" ?

I want this mount

you need to collect all the mounts from the level 50 trials then it will pop up.

You need all the other shiny horsies first

After you get all the other primal horses a quest pops up to get it from Yoshi-P the Minstrel dude at the bar in Revenant's Toll.

Please note that just like Coil those EX-primals are not excatly content you can just easly queue up for and expect and easy clear when done with DF. Depending on the fight they're actually rather difficult on level 50 and require you and your group to know mechanics and deal with them properly.
Your best bet on farming is running those trials unsyched/undersized on level 60. Makes most fights a 2-4 minute breeze. PF is your way to go!