Of course, these instructions sounded clearer when I was doing it, but this kind is quite easy actually.
There are more advanced ones, more complicated.
This is done with only two strings (same or different colors).
First you have to make what look like bunny ears (little loops) passing one to each side of the chain, then you pass through the second loop one end of the lace skipping the first loop, then you do the same with the opposite lace, taking care that the lace is not twisted, and then you pull tight from the 4 strings at the same time. They kind of slip, so try not to let go.
The longer the strings are the messier it will get, so it will be more difficult.
This is just to keep going, I did not learn how to start it, but there are a lot of tutorials on the internet.