or possbilly the silver metal studs (Standoffs) you simply work out where the holes are and screw in these to match the mounting holes on the Motherboard itself. Or sometimes they are in the format of a Plastic screw in stud which are more tempermental and these have to be firmly but delecately alingned to screw in.
Or some of the lian li have them already fitted. The is no need to put any washers on if they are arround as on the motherboard around the hole where u would put a screw there is a silver shielding which acts as protection from some slight missalign.
So simply screw in the studs and align carefully with the motherboard.
But first fit the rear of the case motherboard I/o Plate shield before fitting the motherboard.