You can't really have two separate accounts 'logged in', other than fast user-switching. But it depends on what you mean by logged in of course.
You can easily run applications as another user.
If you right click while holding the Shift keyboard key on a shortcut or executable file you will be given the option to 'Run as a different user'. Provide the required credentials, and the program will start. You could start a Powershell or CMD window as another user. Any program you launch from those shells will run as the alternate user.
This mostly works with a few exceptions for applications designed to only allow a single running instance on a computer (Firefox, Chrome, Sublime Text, etc).