If you go to the website using your computer, there is an icon that will allow you to attach an image to your message. You cannot attach an image using your phone. There are tools in the detail section that will assist you in reducing grain. Please clarify which version of Lightroom you're using. This forum is directed towards Lightroom CC, the new cloud-based version.
Grain (called more commonly noise in digital photography as it is unrelated to grain in film photography in its cause and appearance) is fixed using noise reduction in the detail sections in Lightroom Classic's develop pane or in Lightroom CC's detail section in the adjustment sliders. The same can be done on the mobile version of Lightroom. I recommend you watch a few youtube videos on how to use the sliders in Detail.
If you go to the website using your computer, there is an icon that will allow you to attach an image to your message. You cannot attach an image using your phone.
Off topic here, but I thought I'd point out that you can, in fact, upload from your phone. You have to turn the phone sideways into landscape orientation, and then the icons for adding images appear in the interface.
Thanks for pointing that out, Michael. I guess if I used a smart phone I might know that. I have just been going by what others have said in the past. It's not that I don't like smart phones, I just cannot use them.