From TechNexion Developer Portal

Boot Configuration Settings: PICO-IMX8M

Settings for PICO-PI Baseboard

Below is a picture representation of the boot configuration jumper settings for PICO-IMX8M on our PICO-PI baseboard. Configure the jumpers according to the boot selection you need.

There are two main boot configuration settings: Boot from EMMC, and Serial Download Mode.

Note that on PICO-IMX8M, the default boot media is EMMC. On the module, we configure boot configuration signals to boot from the default media without needing to be pulled high or low on the baseboard. You can either leave the jumpers as set here, or remove them.
PICO-IMX8M EMMC Boot Configuration

In serial download mode, the PICO-IMX8M-MINI will look for commands to be sent to it over USB OTG. This is used to load new software onto the unit.

PICO-IMX8M Serial Download Mode Configuration

Settings for PICO-WIZARD Baseboard