I'm always suspicious of somebody with one post... but...
If you are looking to gain weight via MUSCLE (which I don't think you are, based on your post) then the lifting weights is required.
But the easiest way to gain some quick size/weight is starchy carbs plus drinking lots of water. So rice pudding, brown rice, oatmeal... plus lots of water. The carbs will help you store water and you will very quickly gain "water weight".
If you are looking to gain weight via MUSCLE (which I don't think you are, based on your post) then the lifting weights is required.
But the easiest way to gain some quick size/weight is starchy carbs plus drinking lots of water. So rice pudding, brown rice, oatmeal... plus lots of water. The carbs will help you store water and you will very quickly gain "water weight".