Have a look at your seat. There is a plastic cover all arround it base.
And probably, also you ´ll find structure bars underneath the seat.
Perfect! So very easy trick.
Pull out the stretcher between the seat and it plastic cover and grap the frond edge of the cover about 3cm inside the nylon.
Weel you got one side done!!
Now your seat cover is handled with 4 grap points. This will avoid the seat cover to move or slide.
You got it?