That SATA port is what you need. You can use that to connect an external eSATA drive enclosure (external jbod).
For a clean install, get a SATA to eSATA adapter - the kind with an expansion slot plate. Something like a STCESATAPLT1LP. Unscrew the eSATA end from the plate, cut a matching hole in the PC case and mount the port to the hole. This is better than going straight from the internal port in my opinion.
It looks like you have a mini-PCIe slot as well, probably intended for WiFi. That may work with an mSATA to SATA adapter to give you a second port. Or it may work with an mSATA SSD. I would test with something cheap or get confirmation it works from other users of this PC before investing in an expensive SSD.