how can i copy and paste from my mac to my iphone

See the following: Copy and paste between devices from your Mac - Apple Support

including this note in that article:

Note: To use Universal Clipboard, your devices must meet Continuity system requirements. They must also have Wi-Fi, Bluetooth, and Handoff turned on in System Preferences (on your Mac) and in Settings (on your iOS and iPadOS devices). You must be signed in with the same Apple ID on all your devices.