I am looking for an article or video which explains how the normalization in the limma voom is performed. I looked for some articles but I could not find any which explains it clearly. Can someone help me in this regard?
A good place to start would be to look back to where limma was originally used, i.e., for microarray analyses and microarray normalisation, and i highly recommend Professor John Quackenbush's great paper on this: http://www.cs.cmu.edu/~zivbj/class05/reading/norm.pdf
Then I would read-up on linear modelling and linear regression, as limma is fundamentally based on linear modelling.
Finally, with that under your belt, I would read the actual work by the 'new' limma authors:
Part of being a great researcher is being able to read and understand your colleagues' published works, but I can understand that entering a new field can take time when there are literally 1000s of articles already out there on the topic.