The relationship is a mutualism. The fungi benefit from carbohydrate delivered to the root via the plant phloem. The roots benefit from water and mineral import by the fungal mycelium. In such slides you should be looking for typical soil-root anatomy and the location of fungal mycelium. You already know what to look for in terms of root anatomy.
Fungal cells are much smaller than host cells, and appear as small tubes with stained nuclei.
Many fungal cells in an area would look like a pile of lumpy spaghetti. The ectotropic slides are labeled as cross sections. The endotropic slides are also labeled as cross sections. In another mutualism we are looking for plant root anatomy in association with another organism. Again, you already can recognize typical soil-root anatomy.