looks like you have not put the HotPot files in the right place on your server
When you download
the HotPot module from the plugins page on Moodle.org, you get a zip file. You need to to unzip that file and inside you should find a folder called "hotpot". Upload
that folder and its contents into the "mod" folder on your Moodle site, to create a new folder at "mod/hotpot".
Now go back to page where you found the error before, and this time the message for the HotPot module should say "to be updated". Scroll to the bottom of the page and click the "Continue" button. The installation/upgrade should then begin.