If you are in the motion of installing Moodle then we have to assume the plugins are necessary and are somehow missing from your moodle installation, and I would guess that your moodle download was faulty.
you will have to download from moodle.org a fresh moodle and start the downloading and installation process again. I must admit I haven't come across this particular problem on installation.
Wait for an expert on this one, as I haven't experienced the above situation.
If you were already in an installed moodle, and were attempting to install a plug-in then try going to your administration to plug-ins and download the stated add-ons (plug-ins) and install them.
Alternatively go to your files and, follow the paths stated above and delete them. Then try clicking again, it should state success.