May I inquire as to what is the difference between the original Interpretation and the application of a particular passage?

I have always (even as a futurist) been bound to the idea that an application CAN NOT be determined UNLESS FIRST discovering the original interpretation as it was understood by those hearing what was either written or spoken to the group or individuals that first heard it. Am I wrong in believing this? And if so, please explain how I am wrong. Thank you.

For example, these two verses from the introduction of Paul's epistle to the first century Thessalonians:

1 Thessalonians 1:1 - Paul, and Silvanus, and Timotheus, unto the church of the Thessalonians which is in God the Father and in the Lord Jesus Christ: Grace be unto you, and peace, from God our Father, and the Lord Jesus Christ.

1 Thessalonians 1:7 - So that ye were ensamples to all that believe in Macedonia and Achaia.

The original interpretation, for me, of 1 Thess 1:1 seems to be fairly straight forward. The authorship is being declared as Paul, Silvanus, and Timothy (abbr) - although I am pretty sure Paul is the spokesman for that group of three. They simply wish them grace and peace.

The application, for me, is fairly general in that we too, when writing to a church (that doesn't happen much with me), should wish good things as well. Perhaps it could even be applied when speaking to another Christian. I don't think this would but out of the ordinary but there are probably better texts that would express this kind of positive interaction.

The original interpretation, for me, of 1 Thess 1:7 is also fairly straight forward. The individuals from that 1st century church at Thessalonica were good examples to those other believers who were in Macedonia and Achaia at that time.

The application, for me, of 1 Thess 1:7 is that we also should be good examples to other believers from other churches as 1 Timothy 4:12 expresses as well. There is no way possible that I can be a good example to believers who existed back in the 1st century and neither should I need to fly over to Macedonia and Achaia to see if there are even existing churches there. I should be a good example to unbelievers as well, but this application cannot expressly be taken from this passage of Scripture. There are much better texts than this like Luke 6:27-31.

So, what is the difference between original interpretation and application?

and

Is it true that the application for us can only be determined by first understanding the original interpretation? And if not, what is it exactly that we must we understand in order to make proper application to our own lives from a specific passage?