In case you are using the Steem-JS API, you will find all you need at:
https://github.com/steemit/steem-js/tree/master/doc#broadcast-api

For example, broadcasting a Steem post or comment in JavaScript is as simple as:

steem.broadcast.comment(
    wif,
    parentAuthor,
    parentPermlink,
    author,
    permlink,
    title,
    body,
    jsonMetadata,
    function(err, result) {
        console.log(err, result);
    }
);