Hello,
Thank you for posting in Q&A forum.
I can see that you are installing the OS in the drive. If you want another partition, please kindly select the drive where you want to create the partitions and click on "Drive options (advanced)". Then you will be able to see options to delete, format, and create partitions.
To help other customers who may be facing the same issue, please don't forget to vote if the reply is helpful.
Best regards,
Jill Zhou