Well, the immediate answer is no, you shouldn't stick driftwood you found outside right into your tank, because it's undoubtedly full of microbes and bacteria that will quickly infest your water and make your little guy sick(unfortunately, I've made this mistake...). However, you CAN use it in your tank if you're willing to put a lot of time and a bit of work into it. Here's a link to an article about what you'll have to do. http://bettafishy.com/how-to-make-yo...ium-driftwood/
Make sure that everything you use (the brush you need to scrub the wood, the container you use to soak it, ect.) has been sterilized with boiling water only! I just started some nice pieces I found on the beach soaking yesterday, so in a few weeks they'll be ready for a new aquascape!