Connect to "gold plate" connectors of existing PCB
The way they are supposed to be used is with "pogo pins" (sharp spring loaded pins) mounted in a test fixture that holds the board in place against the pins. Such a fixture is known as a "bed of nails".

Great for production but kinda sucks for development. Building such a fixture for one-off use would be a lot of effort and may make access to the board for test probes difficult. Especially as those pads are nowhere near the mounting holes.

Solding wires to the pads is an option and probablly what I would do personally. I would go for 30AWG wirewrap wire, if the wires get accidently stressed you want it to be the wire or the solder joint that fails (as those are easy to replace), not the pad.

Depending on the physical constraints an option can be to glue a connector to an empty part of the board with hot glue or silicone rubber and then solder your wires between that connector and the pads.