Download and install the Raspberry Pi Imager on your Windows 11 computer. Flash a new microSD card with OctoPi from Other Specific-purpose OS, 3D printing, OctoPi, OctoPi (stable). Edit Settings and fill in the fields (I suggest leaving the username as "pi", pick your own password), don't forget to select the WiFi country. Click on Services and enable SSH, Use password authentication.
Boot the Raspberry Pi with this microSD card. If you do not have a monitor attached, give it a few minutes as it will reboot itself a couple of times. Then connect with a browser to http://octopi.local. If this doesn't work, then go your LAN/WiFi router and determine the IP address assigned to the RPi and browse to http://ip.add.re.ss.
Complete the first time setup. Note that the username and password you set here can be different than the username and password you set in the RPi Imager. The Imager set is used to login to OctoPi and the ones you set here are used to login to OctoPrint. You will have to remember both sets.
Let us know if you are successful or if you need more help.