Firstly, tap the 'trade' button on the home page:
Select the 'recurring trade' option:
You will now be able to select the frequency. As shown below you can select hourly, daily, weekly or monthly trade options.
Next, you can enter the amount you wish to exchange on a recurring basis.
To switch the currency, tap the double headed arrow icon ' < - > ' between the two currency images, which will allow you to either convert your fiat currency into BTC or vice versa.
In this example, we entered £50.
Please note, your account must be funded for the recurring trade to go through. If your account balance is too low it'll skip to the next time or date until your account is funded.
For information around funding for recurring trades see this page.