To use promo code, follow the below steps-
Step 1: Sign in to your Techpacker account.
Step 2: 
Slide out your side menu by clicking the icon on your screen's top-left corner. 
Under accounts & settings click on 
payment method.
Step 3: You will be directed to the payments page. Click on the Update plan button as shown below.
Step 4: Select your plan and click on the Continue button.
Step 5: Type your promo code in the box. Click on the Confirm button and it's done.