Programming BMW e88 key

[mothh]

Hi, I have a 2009 120i convertible and am looking to get a second key made at home. I have found out my key frequency and a seller for a programmable key at that frequency but before I buy it I want to know how to program the key. Ive seen multiple videos and threads where people mention using ignition or the unlock/lock buttons but in my case because its a convertible and 2009 there is no key being moved to ignition and back and if I hold unlock it will just open my roof instead.
One method ive seen that seems more likely is where they mention using a key logo on the steering column and using the original key in the slot to program the new key. I looked around on my steering column but I dont see any key logo like what ive seen in the videos.
Does anyone know what to do or have any ideas? (I am not going to dealership for this because they quoted me $800 for a spare key and private is offering $600)

[Spools]

Would love to know this for myself. Ijust bought my first BMW; a 2009 E82 N54. It only came with one key. I bought a pair of used keys off eBay. I made sure they were 315Mhz on the back like mine. That's what y'all mean by matching frequencies right?