How do I connect my 2009 MacBook Pro to my iCloud storage?

See instructions in Use iCloud Drive to store documents on your Mac and iOS devices - Apple Support

(Change the version near the top of that support article to your version or as close as possible)

Note the you can use iCloud Drive in Finder on your Mac without turning on Desktop and Documents as described in the "Store your Desktop and Documents folders in iCloud Drive" section of that support article. Don't turn that option on without fully understanding it.

To what part of iCloud storage?

Photos: Set up and use iCloud Photos - Apple Support

Data files: Set up iCloud Drive - Apple Support and Add your Desktop and Documents files to iCloud Drive - Apple Support

Contacts: Set up iCloud for Contacts on all your devices - Apple Support

Notes: Set up iCloud for Notes on all your devices - Apple Support

Other?

Use an internet browser to view some iCloud synced data: www.icloud.com