Before discussing how to make TwelverShia.net more popular, it should first be discussed what the vision for the website is. There are many directions that this community could go in, and they all have different implications. Right now, I see perhaps 3 different options, although I am sure that others exist.
Vision 1 - TwelverShia.net should be a large and recognized "brand" in Sunni-Shia issues. For this vision, TwelverShia.net would probably want to expand and diversify. Perhaps, a YouTube channel should be established with lectures, propaganda videos, etc. Likewise, there should be other diversifications into various other Social Media venues such as Facebook, Twitter, etc.
Vision 2 - TwelverShia.net should be a segment of a larger project that is aimed at improving things for Muslims. In this case, the same diversification should occur, but with a different purpose. Perhaps some partnerships could be made with other groups such as a general purpose Islamic forum, or various lecturers that can give lectures on this topic.
Vision 3 - TwelverShia.net should remain much the same as it is, with a Web-Site full of articles and a forum with Sunni-Shia discussions. With this vision, the key is advertising, advertising, advertising. Advertise all over the place. Have everybody tell their friends, their family, etc. Create some fliers that can be handed out.
What do the creators of this website see as the vision for it? Where do they want this community to be in 5 years? What do they want to have accomplished?