Just use the Reply button and that input field, to Reply to something you feel you can provide info for. There also are tools for the input boxes, but most times, you can paste a link directly and don't need to use any special tool. I will use bold and italic to emphasize, especially if I copied something and want to show which part applies to why I copied it for reference. I've also found that providing the link to what I used for a resource is polite, and to help people help themselves is better than constantly reiterating what they could have found on the web if they just looked, such as IRS resources. Things change, so they should learn to use the resources that are maintained for that purpose.

And be prepared to be a bit frustrated. A lot of times, we don't get enough info and sometimes, even though we ask, they don't provide that missing info. We've all gotten pretty good at mindreading.