Super noob question - Addons (WeakAuras)

Ok so i am returning player to WOW after almost 15 years of not playing at all. I have downloaded the retail trial version to jump back in to get reacquainted with the game again. I will probably get a subscription again after the level 20 trial cap. Years ago when i played I had a bunch of addons i used. I came across WeakAuras as a good base UI but i've had a problem getting it in game. I have followed the instructions to get WeakAuras added to the addons and i see it there and have actually imported a frequently used weakaura into the addon. For whatever reason i don't see the UI on my screen but the addon appears to be loaded and enabled. Am i just an idiot for not figuring this out? When i launch /wa in game i can see the UI pop up but as soon as I close the settings box it disappears. Any help would be much appreciated.

Also - any recommendations of where/which game to jump back into after all this time? Finding a starting point with all the game versions and expansions is overwhelming. Thank you!