In most cases you won't need any computer. See: If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support
If you do need to use a computer, you can use a Windows PC with iTunes installed. See the following from can I use my asus laptop to reset my ipad? - Apple Community
This process requires a Mac or PC. If you're using a PC, make sure that it has Windows 10 or later, and that iTunes is installed. You also need the cable that came with your iPhone, or another compatible cable, to connect your iPhone to the computer.
If you don't have a computer and you can't borrow one, you need to go to an Apple Retail Store or Apple Authorized Service Provider for help.