Need Aperture help...

[Starbright]

I am new to Mac and, of course, new to Aperture.

When I try to download photos off my card by card reader, they show up in Aperture, but then when I remove my card reader w/card, the pictures disappear from Aperture too. I am sure there is a step I am not performing, but I have read and read and can't find any info basic enough, or step-by-step enough, to help.

I am very frustrated and need some help.

Thanks in advance.