DC Power Jack
By convention, pedals use a 2.1mm barrel connector for power, with a center negative supply.
Getting the polarity correct when wiring jacks is often a point of confusion and failure for many newcomers to DIY pedal building. Luckily, it's not a concern for this kit since the PCB takes care of it for you.
Insert the DC jack into the PCB and solder it into place. The holes are spaced to provide enough resistance to hold the jack, but if it wants to fall out, bend its lugs slightly so they grab onto the PCB more securely, or use some blue putty to hold it in place.
Need a Power Supply?
If you need a power supply search for "9V center negative DC supply." There are fancy multi-bank isolated power supplies for pedal boards, but unless you know you need one, just start with an inexpensive wall plug (approximately $10).
Check the results carefully since most consumer electronics devices use a center positive supply. Guitar pedals are a strange outlier, utilizing center negative.
Battery (not included)
Batteries have fallen out of favor for guitar pedals. In most circumstances, they're less convenient, more wasteful, and worse for the planet. In some cases, though, they are useful or even essential. As such your jack PCB has the option to install a battery clip (not included). Visit the support forum if you need help with this.
Otherwise, just ignore the "BATT+" and "BATT-" pads.