Countries are increasingly introducing Computer Science (CS) as a mandatory subject, but access does not ensure that all students are included and can succeed. Culturally Relevant Pedagogy (CRP) is a theoretical framework that aims to make learning more equitable. It encourages the incorporation of learners' cultures and experiences and emphasises the development of learners' critical consciousness to equip them to address societal inequities. Research in the UK has started to localise CRP theory and practice in CS classrooms and has highlighted the need to overcome bias in lesson resources. To address this, we have conducted a pilot study with 13 primary teachers, co-creating culturally adapted CS resources for their classrooms. This paper describes the first step of the resource adaptation study, a teacher professional development (PD) workshop, and reports on how attendance affected participants' confidence, attitudes, and perceptions of CRP for CS. We also introduce a knowledge appropriation model to reflect on teachers' experiences of learning about and implementing CRP in their computing lessons. After the PD, participants reported statistically significant improvements in their confidence in adapting computing resources to be culturally relevant for themselves and others. Qualitative responses identified important first steps in knowledge appropriation in terms of raised awareness and increased understanding of CRP in CS. The PD resources presented can be reviewed and built upon by other researchers to investigate whether CRP can be introduced to teachers in other contexts and outcomes compared to our findings.