I want to download its software how can i do it?

By software do you mean the phones software/firmware?
If so...
you will need to download EFS, find that here and an alternative version here (use this one if your pc flags the first one as a virus)

• First, on your pc's desktop, create a new folder by right clicking in an empty space and choose new - folder, name this LGAPP or something that you will remember.
• Now open the EFS program, but don't connect your phone yet. You will see a large empty screen with an "explore" button on the top bar, press this.
• A smaller empty box will open in the middle, click cancel on this one.
• You will notice that the screen is now split into 4 sections. In the bottom half is your Pc's files, the top half will show your phones files once we are connected.
• In the bottom left section, find your desktop where you saved the new file that you named before. Open the desktop folder and then open the newly named file, the bottom right section should be empty.
• Now, put your phone into "Data mode" by going to Settings-Phone settings-Connectivity-USB connection mode-Data mode. Return to the home screen.
• Now on EFS close the first window so you are back to the empty screen with the explore button at the top. Click "explore" again, the small empty box will reappear.
• Now when you connect your phone you will have about 3 seconds to tick the box that appears in the top left of the small box and then hit connect in the bottom right of the small box. If a warning appears and says something about a port, just disconnect and reconnect your phone.
• Once connected you will see your phones files in the top half of the screen.
• Make sure that the bottom half is still showing the folder you named earlier.
• In the top half, right click LGAPP and click re-name, LGAPP(text) should turn blue. Now type TOTO and click in an empty space until it is no longer blue
• Right click TOTO and choose refresh. This enables you to copy the protected files in your phone
• DO NOT RENAME TO SOMETHING BLANK!!
• Your phone will disconnect itself
  
• You will get a yellow screen don't panic, just reconnect
• You will notice that a "ghost" LGAPP folder has appeared, ignore it
• Now right click on TOTO and choose "read", after a few seconds your files will start to copy to your pc, this will take about 40 minutes, so sit back, go watch tv or somethin just don't turn off your pc or your phone, in fact, don't touch either.
• Once this has finished you will have a copy of your own firmware backed up. Save this at all costs, put it on a memory stick or something.
• In the top left section scroll all the way to the top and click the folder with no name (very top one) you should now see TOTO again in the top right section.
• Right click on TOTO and rename back to LGAPP, then right click and refresh again.
• Now click on "Disconnect" on the middle bar and choose "yes" from the pop-up. Your phone will now reboot. Thats it your done.