you have to have them stored someplace (I use Imgur) and post from there.
Tweets you should be able to simply right-click the Tweet and paste into your post. For example, I just copied the address line from this twitter page and pasted:
God only brought one guy back from the dead on Easter. Trump is here to bring back the whole economy on Easter 2020. Enjoy this clip (possibly, like, the best ever), share and be sure to subscribe to Making Podcasts Great Again (@TrumpPod) – new every week! pic.twitter.com/aUifVWRzfh