Hello Simran , recently I helped my team in establishing the Posh . For this we took help of a organisation named Yourdost . They helped us with the training first to educate the whole team about posh and provided the certificates ,later they helped us in forming the team also for the External member . Now we have included this in our onboarding itself , whenever a new person comes in the team we try to conduct their posh training on the same day .
Hope this helps you !