how ti delete pictures on my icloud

If you are using iCloud Photo Library, then see the "How do I delete photos and videos from a device using iCloud Photo Library?" section in:

Get help with your iCloud Photo Library - Apple Support

Be aware that iCloud is a syncing service, not simply offline storage. If you delete the photos in iCloud, then they will also be deleted on all your devices signed into iCloud. You may want to archive them to your computer first:

Transfer photos and videos from your iPhone, iPad, or iPod touch - Apple Support

log into iCloud.com from any computer web browser or if yu are using iCloud Photos library delete the photo on any connected device - when you use iCloud Photo Library al changes (additions, deletions or edits) made on any connected device are made on all connected devices - since you provide absolutely no information or context we can only make guesses but most likely the much smarter solution would be to increase your iCloud storage so you have adequate storage for your needs -- Manage your iCloud storage - Apple Support

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