Programming cortex m0+ soic for coustom pcb
Firstly, you don't have the full datasheet, just the summary. It's available here under "Datasheet," not "Summary."

http://www.digikey.ca/product-detail/en/atmel/ATSAMD10C13A-SSUT/ATSAMD10C13A-SSUTTR-ND/5226466

This particular chip has Serial Wire Debug, or SWD. Search that datasheet for that. Two pins, one for clock and one for data. I would recommend purchasing a programmer. 

http://www.digikey.ca/product-detail/en/atmel/ATATMEL-ICE/ATATMEL-ICE-ND/4753379

Good luck!