^^There is nothing to get confused so dont worry. It is same like installing apps in android / iphone etc.
Symbian apps comes in sis, sisx or normal java (jar) files which are compatible with your phone. You just have the file, copy to your phone's SD card, browse to that location using phone's file manager and click the file to install it. Done.
For you the best way is to check out the OVI store (now Nokia store). There should be a Ovi store icon in your phone. Click that. You need to have a data connection for that. Go to Ovi store, create a account and browse the apps there. Download the ones that interest you. It will be self explanatory when you go there.
Symbian is a no fuss straight forward OS so navigating in the OS is not a big deal.
Yes one thing that you require now are the offline.maps. For that connect your phone to PC in PC suite mode (this is important). Now open the Nokia OVI suite (download if you haven't already, should be 60-100 MB types). Let the OVI suite detect the phone and after it is done, go to maps part in the ovi suite on PC and install INDIA maps.