Here are a few ideas without you having to make drastic changes to your dietary habits.
You can eat an orange rather than drinking just the juice. The pulp contains the fiber.
Eat all of that apple. Eat whole fruits. The seeds and skin contain the fiber you need.
Do not peel your potatoes. Rather than peeling the potatoes, include the skins - that is also where much of the nutrition is found.
Shop for whole grain breads. Whole grains contain the fiber that is normally processed out of white flour.
When you make beef stew, be sure to add more vegetables. The stew meat does not contain any fiber, so add a few more vegetables or even some beans to your stew to improve the fiber content.