To place an NRML buy order,

1. On home screen. search the stock you wish to buy

2. Once you have clicked on the stock you want to buy, it will take you to the page with the details of the stock like charts, news, etc. On the top right corner select the exchange (NSE/BSE)

3. At the bottom of the screen you will see an invest-trade switcher. Select 
Trade intraday and click on buy button. You may be prompted to enter your password in case you are placing the first trade of the day / making first fund transfer of the day

4. Enter the number of shares you wish to buy

5. Under 
Buying Price choose the order type as limit order by clicking on 'Set Price Limit' or market order by clicking on 'Market price'

6. Ignore the toggle that reads MIS and Cover

7. You can see the margin required and available margin on the bottom left of the screen. You can also check the order summary by clicking on view details on the bottom left

8. Swipe right to place the order. On the order confirmation screen, click on view orders button to view your order in the order book