Create yourself a hello world html file , save it and call it hello,html
Upload it to the html folder.
goto your url and add on /hello.html
eg
www.mydomain.com/hello.html
If the page displays , you have it right. if not move it somewhere else
Delete the hello.html.
Find the plugin you are interested in.
Download it
expand the zip
Some are structured like
¦readme.txt
¦upload
¦¦ sub folders of upload
¦install.xml
You only need to upload the subfolders of the uploads. There will be onces like SRC ( If XF2 )
Goto your admin panel , it should be there then