If you don't have a Flickr account yet, create one.
Go to your profile and on the "Connect" tab set your Flickr user ID. Use idGettr to find out what your user ID is.
That's it. Now whenever you go on a trip just post anything you want to Flickr. If you want a photo to be associated to your trip, just tag it with "travelist:trip=TRIP_ID" (replace TRIP_ID with the ID of your trip) and it will show up on your trip's page, on the "Photos" tab.