My 2009 E90 came with the smoker's package with a 12V cigarette lighter and ashtray along with the standard 12V accessory outlet in the armrest.
I had seen several references to a 12V accessory outlet in the passenger footwell, but all my car had was a hole where the outlet was to go. After I replaced my head unit with an aftermarket double din, I removed the ashtray and cigarette light to mount my seat heater controls in that spot.
That left me to run the charging stand for my phone from my armrest which I didn't like for a number of reasons. Ultimately, I decided to recontent the 12V accessory outlet in the footwell. I have seen posts giving quick descriptions on how to do this, but not an actual DIY. It's fairly simple, and should take less than an hour.
61 34 6 973 037 plug-in socket
61 13 1 362 868 cable socket - female (x 2)
61 13 1 351 144 plug housing
The cable socket and plug housing aren't actually necessary. If I was to do it again, I would just use standard flag connectors to connect the wire to the plug-in socket.
First step is to remove the two T20 torx bolts holding the panel behind the glove box in place. There's one on each side. The left one pictured below.
After removing the screws, you can access the mounting hole for the 12 volt socket. The socket only mounts one way and you just have to push it in.
Next, you need power. There are several ways to do this. You can tap fuse 8 as the fuse box is right behind the glove box. In my car, there was a molex connector in the centre console where the cigarette lighter and ashtray light had originally been connected. I just used that connector for my power:
Then I just ran the wires back to the new outlet and connected them using the cable socket and plug housing.
Closed up my centre console and the panel behind the glove box and was good to go.