Two possibilityes come to mind:
a) install is a script, which must be made executable before you try to run it. cd to the folder in which the install script is found, and run 'chmod +x install' to make it executable. then try to run it.
b) you must cd into the folder that contains the install script in order to use the ./install syntax (the ./ means "in this folder" in bash shorthand). Or, from anywhere in the directory tree, give the /full/path/to/install, and it will run (assuming it is executable).