Is there a truly user friendly guide on how to handle iOS Certificates and Provisioning Profiles? – Xcode 7.3 / iOS 9.3
It's hard to know what specific step you're stumped on - since an error signing development builds will cascade and cause issues when you upload. Uploading can have new issues if you don't have problems running development builds.

The outline I use is:


https://developer.apple.com/support/code-signing/


It breaks down the steps to code signing which also deals with profiles. I'll assume you are set up with a proper app / bundle ID in iTunes connect. If that needs guidance, you can refer to this diagram from https://developer.apple.com/library/ios/documentation/IDEs/Conceptual/AppDistributionGuide/Introduction/Introduction.html



The green boxes are the iTunes Connect portions you need to accomplish in the web app or iTunes Connect iOS app.

If the full process is too much, just focus on breaking up the process into smaller chunks or try reviewing the quick start guide.

Worst case, if you don't have the time to work through things - you could see about partnering with another developer or paying someone to help you set things up. If you want to focus on the coding - outsourcing the management to someone that's already done the learning and has a handful of apps through all the steps can probably save you time struggling with things that don't in the end make a better app but help you navigate the systems for submitting apps.