There is no official means of accessing data on WhatsApp. However, it's possible to access publicly available links and announce yourself as a social science researcher.
Search online popular WhatsApp groups in your country (chat groups and media articles)
Join the group and announce yourself as a researcher planning on analyzing the posts for social science purposes
Starting in 2018, WhatsApp funded a number of projects to analyze misinformation on its platform globally. All projects used their own data, not provided by WhatsApp. Here, you can find a list of these studies, which might be helpful examples.