Getting started with FM Go is as simple as moving your solution.fmp12 file(s) to FM G0 12 on your iPad using iTunes or sending the file(s) by email. But that is just the beginning. You will find that most of your layouts will need to be reformatted somewhat because of the smaller screen size. And a limited number of the scriptsteps do not work on iOS. To guide you through these and other aspects, I suggest that you read through the Development Guide and Tech Brief found under the FileMaker Go 12 link on this page first: http://www.filemaker.com/support/product/documentation.html
In Filemaker 12 are default guidelines with an orange color to show the dimension of the various device screens. If you are using an iPad and a desktop or a laptop, you can use just one layout size for all sizes by using the smalles one.
For starters with more to come, select the horizontal iPad dimensions and use that for both iPad and desktop. One glitch, list and report layouts need to be sized about 5 pixels narrower.
You can determine what script steps MIGHT cause problems with IOS (or IWP, etc) by using the popup menu at the bottom of the script steps area on the left size with you select a secript step. There is an otion for IOS. When that is selected, the steps that won't work are dimmed in the selection area and in your scripts.
Oh, when you are designing for IOS, open the file remotely on the IOS device and run it while you are designing it in Pro. You can see the changes immediately and how your screen size adjustments work, etc. The new 12 themes look better on the Ipad than on the destkop...