It depends on the device you are using. I tend to post via my phone buy the principle is the same thing.
See the white arrow (next to Thom's head)on the first screen shot? Clink on it and another pop-up will appear, see second screen shot. Press 'copy link'.
Go to post reply and simply paste link to your post then press 'post reply'.
Remember listening to my fathers vinyl copy of this and Oxygene aged 10 and being utterly mesmerised... Its probably responsible for getting me "into" music, well this and Kate Bush but that was a little later.