Hi Learning on the job,
You can update the employment type by going to the employee details screen then go to Tax File Declaration, scroll down to Employee Type then select to part-time.
You can then update the pay rates by following the steps in this article.
https://support.yourpayroll.com.au/hc/en-au/articles/200265374-Updating-Employee-Pay-Rates
If you have further questions please do not hesitate to let us know.
Have a good long weekend!