How can I store my pictures externally, but access them from anywhere?

I am trying to organize my pictures with my mac and iphoto. I love using iphoto, but am hesitant to store my pictures on the internal storage. I have a 500 gb time capsule as well. How can I store my iphoto library externally, but still access the pictures from anywhere, being either on my laptop or desktop? I’m trying to future proof this solution as well, like, what do I do when the external drive fills up? Thanks for the help!