how can i transfer photos from icloud to iphone ?

https://support.apple.com/en-us/HT201313

The link from Panchososa694 should help.

but if you have our photos stored in iCloud with iCloud Photos then you basically just need to sign into the same iCloud account on your phone.

Then go into Settings > Photos > Turn on iCloud Photos.

I would also select the option to Optimise iPhone Storage too as this will prevent your phone from filling up with photos.

• iCloud Photos attempts to store all of your photos on the Phone.
• If the Phone is running low on storage then it replaces some of the images with low- resolution versions. The original Hi resolution version stays in iCloud and will download automatically if you want to view one of the low resolution images.