Combining Videos Together
You will need VirtualDub (free video editing software) to combine videos together. I have used it in the past to combine videos together from Fraps to upload videos to Youtube. When opening VirtualDub, drag the video you want to combine onto that window, OR go to 'File' which can be found at the top left of the window and select 'open video file...' it and browse your computer to find it.
Compressing Videos for Upload or Storage
If you're looking to upload this video or wish to reduce the size of it, you may want to compress the video: make it the file size smaller while still retaining high quality. In which case I have another tutorial to reduce the size right here.