The user documentation for your server can be found here. T1s originally shipped with Solaris 8 but Solaris 10 will run on them.
If the system doesn't have a cdrom installed you will either need to get one or have a working jumpstart installation. If you have a working jumpstart server then you will need to speak to whoever administrates it to get it set up for your system.
You need to access the LOM by connecting your laptop to the LOM port with a suitable serial cable and then using a terminal program - screen can do this e.g.
screen /dev/ttyS0 9600 vt100. You may need to change the speed and device in the screen command. Once you have access to the LOM you need to get to the openboot ok prompt enter the LOM
console command to do this.
You should now have an openboot
If you have a cdrom installed and the installation media in it
boot cdrom will boot from the cdrom and start the instalation process.
If you're installing from a jumpstart server
boot net - install will do the trick.