The URL to machform is whatever folder you installed it in. Type the URL in to your browser. You should then see a log in form, similar to that shown in the demo: http://www.appnitro.com/demo/.
The URL to your Machform installation will be pointing to whatever folder you installed it in e.g. http://www.yourdomain.com/machform/
The installer script would have asked you for the folder to install it to, as well as all the other details (including the Admin username/password so you can get into the admin panel)
If you find it hard to get started, try the demo (link above).
Otherwise, you can post a support request to Appnitro (click the Support link near top right of the web site).
There is a tutorial video here: http://www.youtube.com/watch?v=aDFFWtoiJhk