We suggest you use Audacity to work in the waveform of the music file. It's free.
Listen to find the point for a repeat end. If there are repeated percussion patterns this can help. I'll be zooming in around the mid-point of this piece. Visually the piece repeats right in the center.
Here is a break in the wave form. The piece was pre-set for loops. So delete from the end of the empty section to the end of the waveform leaving the first section ready for looping.
Be sure the end of the waveform is at zero or fade it out to zero, the center.
Now all that is left is to smooth the start of the loop with the end of the loop. Select all that's left and copy and paste it it at the end of the existing wave form and repeated at the end of the newly pasted waveform. Make note of the middle waveform's start and Length in "Samples".
Three ways to smooth out the start and endpoints of the loop:
1. fade in the intro and fade out the ending with very short fades like in miliseconds. this may leave a short but noticeable gap.
2. Cross fade by overlapping miliseconds of each after fading in and out using the frist way. Copy all of the track and paste two new copies of the track. Delete sections so one of each section appears in each track. Highlight the section to delete and generate silence to replace it.
The end result
Delete small amounts of the empty space, milliseconds, in all tracks before the middle section, click and hold from top track and drag to bottom.
And same amount of space in only the empty section just before the last wave form. To get it exact copy the blank space in the second wave form before it and replace in the wave form just below it.
Now take note of new start and length of samples in the middle section as that is the part we want to keep. Then select all tracks and go to menu > tracks > mix and render to new track.
Select the middle wave form from the start of the wave to the start of the wave next to and just below it. Menu > Select > Store Selection.
3. Select all of the last track and add a very small reverb effect to the whole wave form to clear out any possible artifacts made in the loop. Select all and apply reverb.
Highlight the bottom full mixed track and retrieve section. Copy that section into a new Audacity window. You should now have a fully repeatable loop. You can add the intro at the beginning if there is one.
If you want to add auto loops with an intro you can paste the start before the looped section. Highlight the whole loop. Put the start and length samples of the loop in the Meta Data of an OGG file format. Export as ogg and save it. The metadata should show up. Add the LOOPSTART and LOOPLENGTH in blank fields or create a new field.
If it still sounds like clipping try extending the overlap where the same wave patterns overlap each other so that when they cross fade it's not noticeable.