Steps
Open Fridge in the bottom bar. It represents the ingredients you say you have at home.
If the fridge is empty, tap the suggested essentials, then Add my selection to save them together. Selecting them alone does not add them yet.
For another ingredient, use the search field and tap the matching result. A search result is added directly to the fridge.
The red area shows where to tap in step 3. Check that the ingredient appears in My Fridge. You can then use Find recipes to look for dishes based on what you have.