1) highlight the Audio file in question
2) count out how many beats are in this measure
3) set your locater points on the LOGIC timeline to the amount of measures that you counted from your original file
4) hit the Loop command on the transport bar so that the bars to be edited are shaded at the top of the Timeline
5) go to OPTIONS > Tempo > and adjust tempo using length and locators -
6) it will then ask you if you want to change the tempo Globally or Create
7) choose your command and the tempo wil automatically be calciulated in the transport bar