I wrap a strap each around the lower control arms and pull straight forward and attached to a cross member on the trailer. These are fixed length straps that are equal in length.
On the rear I will hook into the front leaf spring hanger area and attach at the oppostie side of the trailer at the rear crossmember to create a side and rear pull. So the two rear straps are X'd. These two straps are adjustable in length to tighten everything down.
Once car is tight with straps, hit the e-brake and/or put in gear/park.
What kind of straps and/or hooks do you have on those straps to work with? Look like you could hook to the K frame or control arms and pull forward to the front most cross member, if your straps have hooks.