That wire that you are holding is not the antenna lead, the leads are the 4 on the right(black)
A live feed can be taken from the multi plug on the left top, you need a meter or a bulb to find the live one, its simple to just melt the plastic with the soldering iron tip and solder the digi power led to it, then tape up.
Then the diigi box will turn off and on with the TV on the comand.
The aerials have always been a problem, the only way is to cut one on the end ones on the block of 4, do this about 2" from the plug and splice the lead to a short piece of Coax with a plug on the end to go into the digi tuner.
When joining screened cables take off the plastic about 1" back, pull all of the screen wires to one side and twist, then just use the tip of the soldering iron to melt the inner plastic, the wire is very thin, solder the 2 inners and insulate, then join the 2 screens and tape up. it does not matter if you do the splice inline or with the two cables together and join and tape up the ends