how do I delete iCloud pictures that dowloa in my computer

Go to https://www.icloud.com/photos/ in your Safari browser. Log into your iCloud account and launch the Photos app. There are tools to delete in the upper right hand corner. Pictures that are in the Recently Deleted folder on the left Sidebar, will automatically be deleted after thirty days. Or you can also manually select items, and use the trash can button again to remove them immediately.

Here is a support article that may help: https://support.apple.com/guide/icloud/delete-and-recover-photos-and-videos-mm08b49040b5/icloud

If you are using the Photos app that is installed on your computer running macOS, the procedure is similar. Go into the Recently Deleted folder on the lefthand Sidebar, and then use the Delete All button in the upper right corner of the app.