I do a google image search for something and make sure "gif" or "gifs" is in my search, then most of the results will be gifs.
Then I single click on them until I get to the one that I want. It appears larger.
Then I right click (or press and hold on android)(someone else will have to say how to do this on iPhone), and select "open image in new tab".
Usually, from there, you can copy the URL at the top, that ends in ".gif", and paste it into VolNation. Some sites, like Giphy, have a secondary step that has to occur. You go to the right and click "copy link", and then select the middle link, highlight all, and copy.
After that, just come back to VN and click the image button at the top of the chat window.
Then click the link button, and paste your image, then click insert.
Voila!