That depends entirely on how the guy you paid built the project file. If he built it with the intent for you to swap stuff out in it, he should have placed your audio file in a precomp so that all you have to do is change the audio file in the precomp and then everything links to that.
Click on the tab "SOUND MOUNTAIN LOGO" or double click the colored icon in the layer panel to open up that composition.
Import the audio file you want into the project panel.
Click the new audio file in the project panel to highlight it.
Click the "old" audio file in the layer panel to highlight it. (they are both highlighted now)
Now hold down the `Alt` key and drag the new audio file from the project panel onto the old audio layer in the layer panel.
Doing it this way will automatically make all the necessary connections from the old file to the new file.
Or... you could just drag the the new audio tracj into the "Sound" compositions layer panel.
Select the solid layer that has the Audio Spectrum effect applied to it.
Then in the effect setting panel for Audio Spectrum look for the "Audio Layer" drop down list near the top, click the drop down menu & select the new audio layer.
everything you said has worked so far, thank you :]
but there is still only one problem, i can't seem to be able to sync the "Audio amplitude for logo" to the new track, it is still synced to the track that he gave me the layout with.
therefore everything runs for 4:15mins but the"Audio amplitude for logo" stops running at 3mins (same length as the track it came with) and is out of sync with the beat the whole time :/
There are two audio sources in your screenshot. Turn one of them off. Then make sure that the "audio spectrum" effect is pointing to the correct audio source.
Another problem may be the "Logo and Audio Spectrum" layer. That is a nested composition and you may have to open it up and figure out if there is an audio layer and affect hidden inside that nested comp.