Very simple ! First of you should know that you have 16 nonstatic objects, and a total of 128 objects. This means you shouldn't use those nonstatics (1-16) where you could use statics, if you plan on having stuff move a lil

The 17th object comes as a nonstatic, but you'll need to tick it static otherwise it'll glitch out

You'll need 4 of those nonstatic objects (1-16), and four joints (page 1 tab 2) :

An "anchor", an object ticked static. This is the object your other ones will swing from. it can be placed anywhere it doesn't matter

Two handles, starting and ending wherever you want them, each attached with a joint at their top to this "anchor" object. So if your anchor is 1, and your objects are 2 and 3, "enable" two joints , link 1 and 2 in the first one, and 1 and 3 in the second. These joints should rotate freely on the x axis, so put 1 under x axis, and 5 and -5 in the ranges. /!\ these joints are the center of rotation so get their positioning right

Lastly the seat itself : put it where you want to, and link it to the two handlebars. Then under each joints, put 1 in the z axis, and 999999 in strength. This will lock them in place. It doesn't matter where the joints are as there's no rotations.

This *should* work, and is the basics of a swing, but I highly suggest you try stuff out and really try to figure it out, so you can utilize in the best ways for your situation.

Here's a great study case for a swing : cro_ninja_challenge.tbm by Crocap