Really, I have no clear idea about this topic, so let me know more about it.

Hi, the snowball technique is used to collect additional literature after your have done a few complete ones. It's used to add additional, updated, or important information to your collection. There are different ways to do it but the easiest might be as follows. Look at the reference section in the first few sources you found. See which of the references used can be of use. Then use the reference section of other articles/sources. That is the basic idea behind the technique. I hope it helps.

Snowball Sampling: Definition, Method, Advantages, and Disadvantages

Snowball sampling or chain-referral sampling is defined as a non-probability sampling technique in which the samples have traits that are rare to find. This is a sampling technique, in which existing subjects provide referrals to recruit samples required for a research study.

https://www.questionpro.com/blog/snowball-sampling/