Page 14 of your manual shows where the 12 volt socket is. Below and a bit in front of where you put the key in to unlock your seat. It's a BMW socket rather than an old cigarette lighter type so you may need to switch out the plug on your charger.

 

Thanks, i looked a bit harder and found it. if I switch it to another plug to suit my charger it that ok and won’t do any damage.

 

The plug is a Hella socket and your charger would require a Hella male plug. I don't know if the Can Bus system will accept the CTEK Charger. You could make an adapter to convert your current charger connector to a Hella male. If you take the Hella socket out it is wired to a BMW specific connector that you would have to cut off and replace.

In my case I also needed to be able to run my tyre pump from that plug and the Can Bus won't allow that amount of current either.

So I removed the Hella socket, unplugged the BMW wire from the socket and sealed the end with tape. I then ran a fused(20A) pair of wires to under the battery cover on the right and connected the socket directly to the battery negative and the Positive jumper connecter (the two points you would use to jump start another bike).

The hole left by the BMW hella is a standard and the cigarette lighter socket fits straight in.

This way if I need to sell the bike I can simply remove these wires and socket and return the BMW Hella. plug it in and viola

 

When I installed my Denali Cansmart I also added a CTek connector, direct to battery & Positive terminal. I located the connector under the rider seat. Planning ahead as the bike is fairly new.