You can use the buttons on the controller to start a test program (runs every zone 1 minute), or start any existing program that’s already programmed on the controller. You can NOT create a program using buttons, but you can run an already created program using buttons. Long press button B3 will allow you to enter this mode.
If you just need a custom program that you don’t want to run regularly, a common practice is to create this program and set it to Disabled. That way it won’t run automatically, but using B3 you can start it.
Note that both sensor 1 and sensor 2 support ‘program switch’ feature. Which means you can connect a physical button to SN1-GND, or SN2-GND, and configure it as a program switch. When the switch is pressed it will start a program (for SN1 it starts program 1, for SN2 it starts program 2).
I recommend you to take a look at the OpenSprinkler User Manual:
https://openthings.freshdesk.com/support/solutions/articles/5000716364-opensprinkler-user-manuals
and/or firmware 2.2.0 intro video to see all supported features:
https://openthings.freshdesk.com/support/solutions/articles/5000860920-videos-introduction-to-opensprinkler-v3