Firstly, click the 'trade' button on the home page:
Select the 'recurring trade' option:
Here, 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.
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.
To choose the frequency of your trade, tap the button 'GBP/EUR to BTC: Daily' at the top. As shown below this will provide hourly, daily, weekly or monthly trade options.
Once you hit the frequency and entered an amount, swipe the trade button right to setup your recurring trade.
For information around funding for recurring trades see this page.