To change the boot order, you will need to enter in the BIOS of your computer. Different computers have different ways to enter the BIOS (setup).
Turn on your computer and then look on the screen for some text that says something similar to "Press X to Enter Startup", where X is generally the F2 key or the DEL key.
When you are in BIOS, search for an option that mentions about the Boot sequence and make the boot sequence start with "A" (for the floppy drive), or "D" for the CD-ROM drive (you may have another drive letter assigned to the CD-ROM drive) or USB flash drive/USB device option. Save the changes you have made in the BIOS and restart the computer with the floppy disk/CD/DVD/USB disk inside. Now the computer should boot from the selected floppy disk/USB disk/CD/DVD that contains east-tec DisposeSecure.