How to simulate analogue output sensor with MCP3008 ADC. Can I use a 10K potentiometer with Raspberry Pi 3.3v?
Yes, you can use a pot to provide a variable input to the ADC.

Connect one end of the pot to +3.3V, the other end to Ground, and the wiper to the input of the ADC.  As you turn the pot, the voltage at the wiper will vary between 0 and 3.3 V.