how do i run launchpad?

It's typically (and by default) in the Dock and you can click on it to run it from there.

If it isn't, you can use Spotlight Search (magnifying glass in menu bar or command space key combination) to search for and open it.

Another option is to open a Finder window, use the "Go" menu in the menu bar to go to Applications and then scroll down to the Launchpad app in the Applications folder in the Finder window. You can open it from there. You can also drag it from there to the Dock if you want to add it to the Dock.