How to create this script (for IIS using PowerShell )

I'm trying to do the next : 

1- get the website name (hosted on IIS )

2- Change the physical path credentials (Connect as from GUI) 

I know the command to get the website name it's (get-website | FL Name)

and know how to add the property using Set-WebConfigurationProperty

now i need to do this loop 

get the site name and change physical path credential then go to the next site 

how can i do it