help key grey out and adding effect in CS3

I'm new to this world of manipulating templates and wanted to know if someone could give me some insight on how to adjust settings on a clip I downloaded. I bought the Lightening Strike Revealer clip and downloaded it as a h.264 .mov file. I wanted the lightening to blast then display my text clip underneath it in my timeline. The problem is when I look at it and add it to my Premiere CS3 timeline it has a light grey tint over the file and does not look like the clip I bought. I know that the grey is supposed to be transparent and keyed out when I add it to my timeline but can't find the right settings to key out the grey. I am editing in Premiere CS3 but do have access to AE CS5 if that is what I need to achieve this. I'm not proficient in that software but am about to dive into learning it. Thanks in advance for your help.

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