Okay, take the pointer finger of your right hand and touch the top of your card. Slide your finger to the right until you reach the end of your card, now slide your finger down the backside of your card(where the power connectors are) until you reach the bottom edge of your card. Continue sliding your finger underneath your card towards the pci slot. The next thing your finger touches will be the clip you need to release.
The finger that will release the card should be bumped up against the pci slot, between the card and the motherboard. Depending on how small your case is you may have to use the backside of your finger to depress the clip, rather than the palm side of your finger. Either way, there is definitely a clip there.