There is no guaranteed way to obtain the exact character that the player is hoping for, however through the Wish system players can repeatedly pull on banners containing characters they want (which can be viewed through the in-game banner details) granted that they have enough primogems. Because to guarantee the featured five star on the limited time character banner, a player would need to do 180 pulls which would be 28,800 primogems. A limited time character banner 4* is relatively easy to get since every 10 pulls (1600 primogems) guarantees one four-star character.