Download Reaper, a free audio editing program, by navigating to the download section of Reaper's website. Reaper is free to use but the company does require you to purchase a license for commercial work. Install reaper by running the executable installation file provided on the website.
Download and install VST instruments available from VST Planet's website. VST Planet provides free virtual instruments for artists. A remixer necessarily requires drums, bass and keyboard instruments. Download and install all VST instruments to the same directory.
Download and unpack a remix kit from Realworldremixed, Remix.me or directly from an artist if they provide remix kits. Remix kits provide individual samples from the artist's original studio recording. Some remix kits are more inclusive than others but most of them provide vocals and at least a few clips of isolated instrument tracks as well as key, tempo and licensing information.
Load Reaper from your Start menu, Desktop or by running the executable file located in the directory you chose during installation. Select Options > Preferences > Plug-Ins > VST from the software's menu bar. Select Add from the dialog and choose the folder in which you placed your VST instruments. The instruments are now ready for use in Reaper.
Import the remix kit files by selecting Insert > Media File. Before editing, save the project by selecting File > Save and placing the project file in the same directory as your remix kit.