how can I add my contacts from Apple Watch to computor

Unless you want to do it manually, see the "Set up iCloud Contacts" section in:

Keep your contacts up to date on all of your devices with iCloud - Apple Support

I understand that doesn't really ADD contacts, but that is about all you can do. When you make a change on one device or computer, Contacts updates automatically. Also, if you turn off iCloud Contacts, your information won't automatically move from iCloud back to your device.