>>/34664/
There are two parts of this task:
1) Getting news. You may parse html from site but it is tedious and sometimes hard. Best way is to find RSS feed, they are very easily parsed and created for this specific case.
2) Posting news. If your imageboard has api, it is easy, just few requests. If not, it depends on engine. For example, heavy js sites require complex request automation (sometimes even with headless browser). Simpler engines may have endpoint for http request, it is easy. But I guess with popular imageboards it is not so hard. There is also captcha, but it is another question.
Technically it is relatively simple task, depending on what is written above.