Many of the images at Flickr are licensed for re-use with the Creative Commons license. That means the creator of the image has indicated that the image can be freely reused, sometimes with limitations regarding citation and commercial use. Here are the different Creative Commons license options. You can then search the Flickr images based on those license restrictions using the Flickr Advanced Search page:
For this class, you are using the content non-commercially, and you are probably using the images as is, so you can click the "Only search within Creative Commons-licensed content" box while leaving the other two checkboxes blank.
As an example, here is the Flickr Advanced Search for "cherry blossom" in the Creative-Commons-licensed content:
When you find an image you like, you can click on that image and it will take you to the image detail page which gives a caption for the image and also the name of the image creator. You can then right-mouse click on the image to see the image in different sizes, or you can click on the three dots to the right of the screen to get that same menu option:
When you click on view all sizes, you can see the different sizes available for download. You might find an image that is just the right size, or you can download a big image and resize it yourself. (Remember: a resizing tool can make images smaller, not larger.) Remember to include a caption and credit the creator of the image when you add the image information to your post or webpage.
Cherry Blossom Festival 2008, Washington DC.
Photo by Bart Cayusa at Flickr.
Photo by Bart Cayusa at Flickr.
