If your partner is staying in hospital, she will have 3 meals a day supplied for her. However, the hospital food may not be to her liking. If she is not eating much, because she doesn't like the food, you can take some of her favourite meals in at lunch and/or dinner times (or arrange for family and friends to). You can usually microwave food in the hospital ward, or you could order a take away meal, straight to the hospital (make sure it is nutritious). Alternatively, some gourmet sandwiches or salads may be easier. You can take in fresh or dried fruits and nuts to eat between meals (try to avoid too many chocolates, cakes etc. as these can cause her blood sugar levels to fluctuate).
Once home, (unless you are already there after a homebirth) you will need to supply her meals, at least for the first couple of weeks. You may have a store of pre-cooked, frozen meals that were prepared during the pregnancy. Many potential parents will cook 'double' in the last weeks of the pregnancy, and freeze half (or give them to someone else to freeze, if your freezer is small). Most foods will last up to 2 months in the freezer. If you have been unable to do this, and cooking is not your strong point, try preparing easy meals or order healthy take-away. Family and friends may cook some meals. You may like to set up a roster system for meals (possibly before the birth). Some women become so busy with caring and feeding their new baby that they 'forget' to eat. Remind her to eat and drink regularly, or just place it in front of her at regular intervals.
Some people will 'stock up' on extra non-perishable food supplies, by adding to the shopping trolley in the weeks prior to birth. This avoids you having to rush out and do the shopping immediately after your partner and baby return home. You may wish to do a quick shop for fresh fruits and vegetables, the day before they are coming home. Remember to include plenty of spare baby items, (for example nappies, pins etc.