Dolphin will not load game?

[katex]

I'm new. I've had Dolphin for about 4 hours now.
I've been reading the tutorials (which helped A LOT.)
I downloaded Pikmin 2 and Harvest Moon: A Wonderful Life
I put them on my desktop and they are both .gbc and are both 1.4 GB
and I downloaded Direct X too cuz I heard you need that.
When I open Dolphin and go to double click to start playing they don't work.

I've been looking around this site and others for a while and I've found nothing.
So I might look really stupid when I ask for help here, but please help!
Ive racked my brain for every possible answer. Is it because I downloaded the games wrong? or is my computer not compatible? or is there something wrong with dolphin?
Im really clueless and dumbfounded.
Any help would be greatly appreciated
<3
Much love

[Tomzie]

You must change .gbc file to .iso or It won't play it.

[DacoTaco]

O LAWL

MY FAVORITE TYPE OF PPL