You need to install any of the bengali unicode font to read or write bengali , commonly used unicode bengali font is Akshar . Please follow the instructions to install unicode bengali in your system.
There was no common bengali ascii structure for the old fonts. so each vendors use different bengali fonts with different keyboard layouts. this makes difficult with bengali users as they need to install each bengali font from different websites.
Unicode font is international and has common keyboard layout. Download unicode font for your language and install it on your system.