In most fields, it is an acceptable practice to present published research papers at a conference. However, you will have to check the conference guidelines and and see if they have any specific requirements with regard to presenting a published paper. However, since a conference presentation is very different from a journal paper, you will have to modify the content in a manner that will be suitable for oral presentation. You can change the title of the symposium paper, but I would suggest you cite the original publication. This will serve a dual purpose: it will ensure that you are being ethical and will also help promote your journal paper.