Your post is a bit confusing.
1. Why are you even mentioning a "SATA to USB" adapter cable here? You've obviously built a desktop PC, right? So you can install the desired boot drive, i.e., your SSD, internally in the desktop case, can't you? What does that adapter cable have to do with anything?
2. So I take it you're using the Windows 10 DVD installation disk to install the OS onto the SSD, right?
3. So the SSD and the installation DVD are the ONLY two drives installed at this time, right? No other drives, right?
4. I'm assuming the SSD is a "virgin" drive, right? No OS or other data on that drive, right?
5. So when you power-on the PC does the system boot directly to the Win 10 Setup?
6. If that's not the case, during the boot access the boot options menu by pressing the appropriate F key (as determined by your motherboard - see your user manual if you don't know it), and select the Win 10 DVD installation disk to boot to.
If you want any further info or clarification from me please answer my questions CLEARLY & PRECISELY.