Hi,
There are a couple of ways on how to achieve this. For example, if you wish to submit forms to a SharePoint library, you'll have to publish your InfoPath form template to that library first. Your users can then go ahead and open forms from SharePoint, fill them out and submit whenever they're online. They can download forms and fill them out offline too but you'd want to take into consideration the data connections that are present - as you might know already, forms will fail to connect when offline.
Qdabra has a nice way of handling online/offline submits - there is the Side-By-Side technique which automatically detects whether the form is being accessed offline or online, and then saves/submit based on that.
If you'd like us to help you develop your InfoPath forms, we'd be happy to. Please send email to Support (at) Qdabra (dot) com if you'd like to discuss more.
Best Regards!