Copy dll file to bin folder or add reference?

I need to add third party library file into a asp.net myApp.

After installation, there are 3 dll files in c:\program files\...\sample\bin folder.

Which way is correct so that once I copy to web host do not need to install third party files again?

1) add reference: select 3 dll file from c:\program files\...\sample\bin folder but 3 dll file wil not showing at bin folder, or

2) copy 3 dll files from c:\program files\...\sample\bin to bin folder in myApp. 3 dll files will show at bin folder of myApp.

Question: Do I need to add references? How?
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