To use the Zoho Expense app, first download and install it from your device's app store. Open the app and sign in with your Zoho account. To create an expense report, tap on 'New Report' and fill in the necessary details. Add expenses by tapping 'Add Expense' and input the required information such as amount, category, and date. You can also upload receipts by taking a photo or uploading from your gallery. Once all expenses are added, review the report and submit it for approval if needed. Use the app's features to track and manage your expenses efficiently.