I was taught you should always introduce a new food for three-five days to see if your child has a reaction to it. And always introduce the food early in the day so doesn't interrupt their sleep if they do end up havinf a reaction to it. If it passes the test then you can start combining foods that your child has tolerated.
You start off with enough water to just cover the food. For some reason I always use fresh fruit but frozen vegetables. Boil until you can mash it with a fork. After with the water you used pour food and water into a blender and blend. You are all set. Never add salt or flavoring. The naturals flavore of the food is enough for them. This is easy and cheap and so healthy.
To help ease my daughter into vegetables I add the vegetable to butternut squah or apples and blend together to add some natural sweetness.