You are asking this and tagged as a QBO (online) issue. Simply open your browser of choice (Chrome is preferred) and navigate to quickbooks.com. sign in and you should be back where you started.
If you instead meant you lost the program for desktop QB, navigate to and log in to your camps.intuit account and download your paid for program. Unless your hard drive was wiped your company file should still exist on your computer although you may have to browse for it. Or use a recent backup
Thanks for reaching out to the Community for support. I understand how frustrating it can be when running laptop repairs causes you to lose your QuickBooks, but don't sweat. I can show you how to install in just a few simple clicks.
To clarify, are you using a Windows or Mac computer? I've included the steps to install using a Windows computer below, along with a link for additional steps to install using a Mac computer.