Think about your musical influences. What do you like to listen to? Have you been influenced by more than one musical genre or musical culture? Have you ever arranged a song that contained different musical traditions or instruments? If you have, that's fusion right there.
Decide which musical genres you would like mixed together in your songs. If you're aiming to create and popularize a new genre of fusion music, you should stick to two or three different genres to fuse together in your songs. If you simply like fusion and would like to express your influences in each of your songs, you can make each one as different as you would like.
Choose the instruments that attract you to each of these genres. If you can't play them yourself, you will need musicians who can. For example, if the genres that you are attempting to fuse are Latin and Indian, you can arrange songs which contain percussion played on bongos or congas with a combination of an acoustic guitar or a tres and a sitar as your melodic instruments.
Write your songs and use these instruments and musicians in your instrumental arrangements.
Popularize your new fusion of genres by talking about your new creation. If you do not have a mouthpiece via major press outlets, use your website or your regular update email lists to fill your fans in on the project that you are working on. If you have media attention, use it to its full potential.
Talk about your inspirations and goals when you play live. More than anything, your fans and potential fans will remember this.