I actually only just found out how to do that lol. I did it by logging in to imgur.com, uploading the photo to there, and then selecting the drop down menu to get BBCode instead of the plain link =D
What MoreMoople said. You are unable to upload directly to the forums, but you can post a picture by first uploading to an image sharing site, then using the share links.
... I was going to reply, but it looks like Moople and Krysyy already did. I think I also understand where your question came from, now. I didn't understand at first, as it took me a moment to realise how this case would differ on mobile, from on pc. :P
I often use the tags, except for changing the font, on pc.
[img]putthelinkhere.png/jpeg/whatever[/img] is how you'd put an image. :) Make sure the link you put in between the [img] [/img] tags ends with .png/.jpeg/.whatever, so you know you have the link to JUST the picture, not the page it was uploaded to or so. :)
If you want to upload a picture, you can do so to imgur.com. :)
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