Review on 💡 Enhance Your I/O Capabilities with Songhe PCF8574 PCF8574T IO Expansion Board - 5pcs Bundle by Kevin Lawson

Obtain and read the chip's datasheet. TLDR: It has a register for both reading (input) and writing (output). Pay special attention to the description of weak and strong internal pull-ups when using it for output mode. The jumpers set the i2c address, the leftmost row of pins is connected to 5V and the rightmost row is connected to ground. So if you choose an appropriate address, you now have an available ground and 5V pins to connect to local devices since there aren't any on the top row p0-7. The int pin is available if you want to feed it back to the microcontroller instead of polling for status.