How to update my Google earth software to see the updated maps?

they will be updated automatically and of they dont, then download it again.

The images in Google Earth are updated on a continuous basis. It's hard to say exactly because some areas may be updated more frequently than others (just because that data is more readily available). While most images are no more than 3-5 years old, you may occasionally see an older image. Keep in mind that sometimes older images are actually of better quality than new images (i.e. there might be a huge cloud over a certain area which encourages using the older, clearer image). Google Earth updates every 1-3 years fully- but most of the pictures on Google Earth are updated more often in different areas, so it's usually less than three years old.

not all 2009 maps are on there yet 99% of them are still 2007 and 2005 google earth updates automatically there on just putting on the camera images as long as your internet is on when u open google earth it should update straight away