Question: how do i sign into my icloud photo library?
Answer: On your iPhone, iPad, or iPod touch, go to Settings > [your name] > iCloud > Photos, then turn on iCloud Photos.
On your Mac, go to System Preferences > Apple ID. ... 
On Apple TV 4K and Apple TV HD, go to Settings > Users and Accounts > iCloud. ... 
On your Windows PC, follow these steps.