Jay Garrick (Golden Age Flash) - 1st appeared in Flash Comics #1 (1940).
Barry Allen (Silver Age Flash) - 1st appeared Showcase #4 (1956) / died in CoIE
Wally West (post-CoIE Flash) - became The Flash at the end of Crisis on Infinite Earths
Bart Allen (post-Infinte Crisis Flash) - Became The Flash after Wally vanished / Bart suddenly aged
TV/the CW version of The Flash (Barry) - from The Flash: Season Zero (based on TV continuity)
other (please specify in a separate post)