Hello. My name is***** can assist you with your question.
The initial size of the video will depend on the resolution which it was shot. If you are enlarging it just for viewing on your computer, you should be able to either maximize that window or drag it out to larger window to select the size that you want. You may notice a decrease in apparent quality because you'll be stretching it beyond its normal resolution. But if it is decent quality it probably will be acceptable. If you are trying to record a larger format that will take some other software. If that's the case, let me know and I will be happy to help you with that. Let me know if you have any questions.