To begin, turn on your multi-functional pressure cooker, such as an Instant Pot, and select the Saute function. Next, add some oil to the cooker and allow it to heat up. Once the oil is hot, add the onion and peppers, and let them cook for around 3 to 4 minutes until they start to soften. Afterwards, incorporate the sausages into the mixture, using a wooden spoon to break them up as they cook until they achieve a light brown color, which typically takes about 4 to 5 minutes. Now, add the garlic to the cooker and continue to saute for an additional 1 to 2 minutes, allowing the flavors to meld together. Moving on, it's time to introduce the marinara sauce, water, spinach, pasta, basil, and Italian seasoning to the mixture. Ensure everything is well combined before proceeding. Lastly, cancel the Saute function on your pressure