How does one go about getting tested for food allergies if suspecting gluten or grain?

See a doctor. If you have symptoms consistent with food allergy, your doctor may wish to send you to a board certified allergist for further evaluation for food allergy. This may include allergy testing applied to the skin and/ or a blood test for specific ige to the food. Both have advantages and disadvantages.
Skin, blood, scope. Start your journey by discussing your symptoms as well as your suspicions with your primary care physician. You may not even have a food allergy or gluten enteropathy. Food allergy testing is done either by placing drops of food in your skin or by rast, a blood test. Gluten enteropathy can be detected by blood test (ttg) but upper G.I. Endoscopy by a gastroenterologist is diagnostic.