Man lead my post on amping up your sei. Its super easy i did for the first time the other week. The power cable terminal should fit nicely onto existing bolts that are attached to the positive terminal. For grounding your amp there will be a bolt in the boot just under the carpet to the right of centre.
The Remote turn on seems strange on your HU, normally you have a cable from the back which can be used to turn on your amp where it be a power anntena or proper Remote turn on cable. Have your pluged your head unit straight from the cars connectors, if so it could be a problem. What you'll have to do if this is the case is somehow hook up the remote turn on lead to the switched turn on lead ( i.e red)
See this is why you should use a ISO cable makes life so easy.