not 100% sure what youre after, but if you have the video saved as a file, then software will happily edit it, you would only need a capture card to capture it form source if you didnt have access to the file, but thats quite rare nowadays anyway afaik
most the free softwares claiming to do this arent worth the time though, youre better paying for a proper package unless its a one off (even then if you value your time and sanity it may be worth paying, lol)