Ok, so here's how I made My New Grounds
Leave the frame rate in Flash set to default (12fps) otherwise the video will speed up.
Step 1: Record video, without sound (quality issues) using web cam. ( you can use any other cam so long as you can import it to you computer.)
Step 2: Import video into flash library.
Step 3: It will ask you for the path to the video, this should already be filled out correctly. Hit Next.
Step 4: It will ask you how you want to deploy your video. Select the option to Embed video in swf and play in time line. Hit Next.
Step 5: It will ask you how you want it imported. From the drop down list select "Embedded Video" , the "expand time line if needed" should already be selected, if not, select it. Hit Next.
Step 6: It will ask you what quality, you can select what ever you want, keep in mind that the video is probably going to be a large file size. You may have to experiment with this.
Step 7: Now drag the video onto the stage. It should ask you if you want to expand the time line, select yes.
Now just make sure you lock the layer with the video and make it your bottom layer. You'll do every thing else it the upper layers.
All sound can be imported separate. I recommend this simply for quality reasons. Usually the audio quality from the Camera mic isn't really that great. You might want to record the sound on a separate mic. But, it's up to you, I just know my web cam isn't the greatest. :)
That's pretty much it. I hope that helped a little.