Need help with mounting an Stl on a backing

Hi I have managed to print a logo part of which is a Thistle, but after printing it taking it off the Printer it all breaks into single parts. Can anyone help I need to put it onto a round background or a shield shape background. I havent a clue how to do anything except get files from Thingiverse etc and search for JPG to STL online converter (which is how I got the logo). Any help would be grateful and many thanks in advance for even reading my post