This article shows you how to set up and use Grab Trike using your Android smart phone. I would expect the process to be pretty similar on other operating systems, but this article specifically covers Android phones.
First, go to the Google Play Store and search for grab taxi. Install, following any instructions. If it asks you if you want Grab Trike, say yes.
Once the Grab app has been installed, you are now ready to use it. Make sure Location Service is turned on, along with WiFi (or data service), then select the app.
The app should automatically find your approximate location (enough to be able to calculate the price later) and display it at the top of the screen. Don't worry if it doesnt have the exact street number, as you can contact the driver and tell them the exact address.
Having selected the pick up point, next enter where you are going. As you type, matching locations should be displayed, and you should select the best one.
Once you have entered the drop-off point enter it and you will be taken back to the original map. A price should then be displayed, along with an approximate time for pick up. All you have to do then is press the green 'Book' button, and your trike is booked.
You will usually get a message back from the driver saying he is on his/her way If you need to give further location information you can reply at this point, with for example, the house number and description.
Prices are typically half of what you would pay with a regular trike. For example, to go from my house to SM Mall previously cost 150PHP. With Grab, it now costs 75PHP.
I hope this article was of use to you. As always, any corrections, updates, and comments are welcomed!