When using the App, how can I get the App on the phone to talk to the app on my desktop. For instance, if I start a daily on my phone, I cannot access the daily on my desktop.
There are two main ways to connect S123 to itself:
1) The Inbox feature. This a mobile app native solution that requires the user to have an account to function well, but does its job.
2) You can use something like a Web Map or Field Maps to launch a survey in "Edit" mode. This requires a lot more effort to get right, and also a secondary app.
EDIT: In case there is any confusion here... S123, by default, isn't set-up in such a way to allow what you are describing. That type of functionality will require set-up. That set-up is primarily through one of the two methods listed above.