Tech advice needed

I have dipped a toe into the Twitterverse, but don't know how to get it to work with my other online stuff.  

Ideally, I would not have to post the same thing multiple times in multiple venues read by different people, right?   But I haven't figured out how that works (been nose down in the book for months and months and months...) 

So if anyone can give a plain, simple set of directions for getting tweets to appear here, or things here to appear (in truncated form, I realize) in Twitter...