Hello there, I don't know if you want regular numbers on the abilities themself or an actual bar that has the cooldowns "progress" across so I'm gonna link you the two fairly known cooldown AddOns for you to make your own choice :-)
OmniCC is the one that puts numbers on the abilities.
ForteXorcist is the more visual style with a highly configurable bar without limits.
If those two doesn't suit your needs there's a couple of others but these are the ones I know of.
I use Power auras. My bars are at the bottom of the screen and my eyes are always fixed at the middle so i use power auras to put spell icons around the middle of the screen (stuff like Holy shock) where my character is positioned. It's configured so the icon appears when the spell is off CD, and a timer counting down to when it's next available is shown in its place when it's on CD. Also do the same for bleed effects and ticks/buffs.