I had Lightroom brought for me for Christmas and downloaded it from the adobe website. how can I download it again on my new pc?
The same way that you downloaded it the first time.
Or are you asking something else?
The above link will take you to the Adobe Product updates site. From there you should be able to find the appropriate download for the version of Lightroom you purchased.
If you purchased the Photographers package subscription for Photoshop CC and Lightroom you would have to download through the Adobe Creative Cloud Application Manager.