Different Boosters may be different, but with mine I found it would always go on the second connection.
connect, ignition on and leave switched on for a minute of so for the booster to do a bit of a power trans; then disconnect and repeat and then try and start.
I used to use the booster quite often on my VW LT for the first 6 months or so while I was converting it as the
battery was knackered and I didn't want to replace it until the van was going to actually be in use.
The whole point of the points under the bonnet is to be able to jump start isn't it? so surely they should be good for a booster?