Do you have the Sara-N2 module or is it a development board of some kind?
Generally, you can measure current by using Otii Arc ADC+ and ADC -, you then need to have an in-line sense resistor on the power rail. Connect the ADC+ to the high side of the resistor and ADC- to the low side and AGND to your IoT device GND. The size of the resistor depends on your system peak current. The voltage over your resistor should be between -81.9175 mV and 81.2 mV.
If you have the EVK-N2 evaluation kit, then you can use J103 jumper with a suitable sense resistor and connect to ADC+ and ADC-, together with AGND on Otii Arc expansion port.
By reading the user guide for EVK-N2 it seems like you can power up the evaluation board by connecting J103 (one of the pins, can’t see which one in the user guide) to Otii Arc red main output and the evaluation board GND to Otii Arc black main, and use 3.8V output voltage. But, since I do not have the board here, nor the schematic, it is very hard to give you exact instructions. If you have schematic I can help you further.
Regarding maximum voltage and current, if you have an external DC adaptor, then maximum voltage is 5V and maximum current is 5A peak and 2.5A continuously.