Hi Mary Ellen! Windows computers are just fine for sourcing.
If you have registered for an account at FamilySearch.org, which is free, you can easily copy and paste source citations for the sources you find there. Just find the relevant document, highlight the citation they provide and select copy, then go to your ancestor’s profile and paste it under the Sources heading.
For the Sourcerers Challenge, you do the sourcing of older unsourced profiles, rather than others doing it for you. The project awards owl stickers depending on how many you source.
Sourcing can be a lot of fun!