In more detail
Familiarising yourself with the dataset means becoming deeply immersed in it. Researchers read transcripts more than once, listen to recordings, and make notes on what strikes them, both about individual accounts and across the whole dataset.
Familiarisation is not a step to rush. The notes made here often shape the first codes and remind the researcher later of their first impressions.
In Themescape
Themescape is not used in phase 1. It comes in once coding is under way and the coded data sits in the template.
Where to read more
Braun, V., & Clarke, V. (n.d.). Thematic analysis. The University of Auckland.