If your account is a minimum of level 31, you can request to sticky or unsticky a topic simply by clicking the Message Detail link in the first post of the topic. From there, you should find a button you can click to make a nomination for that topic, along with a text box to add any helpful information about the topic and why it should be stickied or unstickied. Once a topic receives enough nominations, an administrator or lead moderator will look at the topic and the nomination text from the nominators and then decide whether or not to make the change to the topic. Be aware that nominating topics that obviously have no business being stickied can result in the permanent loss of the ability to nominate future topics.