Threading a Brother 760d overlocker looks tricky, so I have included a video of someone doing it. I find that it is easier to actually watch someone and learn from that, than to have someone explain it as that can get confusing.
The manual might be useful for you, but the one I found has to be paid for unfortunately and will cost $10 to download. However, you will find it at http://www.sewingnz.com/brother-brother-760de-760d-760-730d-730-overlocker-instruction-manual/
I have to say that they look fiddly things to thread, but I am sure it's one of those things you can almost do in your sleep once you know what you are doing.
Some things that you might want to be careful of are
- It can be a good idea to set the needle tension before balancing the tension of the upper and lower loopers
- Check for fluff or cotton that can become stuck between the tension plates
- Make sure that tension is not too tight.
- For some reason, black cotton can build up a tension all of its own! If this happens, try a different one.
- It is advisable to use a good quality needle such as Schmetz and check regularly to make sure they are not blunt or bent.
- If your needles touch the looper it may be that the lower looper is out of position. It is always best to check this when you change needles.
- Should the needle plate get damaged so that cotton gets hooked, take a small file or sand paper and gently file it.
I hope that helps, I know overlockers are amazing machines and I am sure you will enjoy using yours.