hello, as an admin you are surelly allowed always to make sticky and announcement topic...while you are posting the topic you will find below the edit box some options...one of thims has the word "sticky"..check it and have fun...or if you have an old topic you can do this to it too..re edit it and check the "sticky" mark...hope i could help you!
É fácil, vais ao fórum em que queres postar o tópico Inamovível, clicas no botão para postar um novo tópico, e abaixo das opções de postagem, aparece-te isto: