Kids will eat when they are hungry and unless you are dealing with an illness or other medical condition that requires specific eating routines, you don't have to worry too much about a child who is not all that interested in food. It is important, however, to ensure that when the child does eat he or she is eating healthy food that represent the different food groups. Forcing a child to eat when they are not hungry sends a message that he or she should ignore their own body's signals which could possibly lead to problematic eating later in life.
If you are trying to encourage a child to eat with the family at a specific time or to ensure he or she eats before an outing or naptime etc... you should observe your child and try to appeal to his or her own personality traits and likes or dislikes. Some children are more interested in eating at the table in a booster seat or high chair without a tray. Some prefer to feed themselves, some are engaged by getting to use utensils like a "grown up". While rounded diets are important, everyone has things they like to eat and things they do not. If your child is not interested in eating, try to find a few favourites that are always appealing or specific tastes or flavours that can be added to other dishes that might encourage eating.
For more tips on eating and kids, check out this page on the American Association of Pediatrics . They suggest nuts as a healthy snack but you should check with your paediatrician about appropriate ages to start kids on nuts and nut products before feeding any to your toddler.