Any editing of data that you do should be committed automatically.
But there is a bug in FM GO that I have reported, but that FileMaker techs have not yet been successful in isolating where changes to data are not committed. The temporary "fix" is to restart the FM GO App. Double click the home button, "flick" the FM GO icon up to close the app, then return to your main screen and re-open FM GO. For me this fixes the problem until the next time that the app gets trapped in this "bug state" as I call it. I've been able to devise a script that, at least for me, has been successful in detecting this state and telling me to restart the app--which I can do without even closing the files that I have open.
For more on this issue and a list of the script that I came up with: GetField returns null in FileMaker Go
Another way is to place a "Commit Records" button on the iPad layout.
Simply changing layouts or closing the file will commit the data provided that it has not been entered into a global field on a hosted file.
But not if this is due to the Bug Issue that I've been trying to help the TS folks here nail down. If your system is in that "state", you can't commit data until you restart the App and try again. That's why I came up with a script that detects this issue and warns me to restart that I've set on multiple files that I use to run when the file first opens. That way I can restart before I get caught editing data only to see it not "stick".
Thanks to each of the responders, I've sorted the problem by incorporating a portal to add records to the 'child' table. I have another problem now which will be the subject of another post. Thanks again.