For those with a poor appetite, liquid calories in addition to whole food meals are often the only way to get the job done. I'd say get at least 3 major meals from food (and note that you CAN train your body to handle more food, just gradually increase the volume of food) and add liquids in between that. Just make up a big blender bomb with
milk (2% up to whole)
ice cream
bananas
protein powder
peanut butter
whatever the hell you like to drink
Mix it up drink it in-between meals to get your calories (but do NOT let it replace the whole food part of your diet, it has to come in addition to the food you're eating).
If someone can find the old McCallum weight gain drink, that's a good place to start.
Lyle