Follow the links,

http://sebastianraschka.com/Articles/2014_pca_step_by_step.html

https://medium.com/100-days-of-algorithms/day-92-pca-bdb66840a8fb

Thanks

You should check: Quinn, G. P., & Keough, M. J. (2002). Experimental design and data analysis for biologists. Cambridge University Press.

The explanation of PCA is fairly simple and complete. The overall book is great and is linked to a web site with examples and data that you could use to run and interpret results.

Thank you

Joanna