how to run VSIXSignTool

following the steps to sign a VSIX package
https://msdn.microsoft.com/en-us/library/dd997171.aspx

step 4 says "... You can now run the VSIXSignTool from the project’s local packages location ..."  

What does that mean? Do I run from the CMD line?

and what does this tool do for me that the signing tab of project properties does not?

thanks,