Bangla Unicode Setup in Windows PC:
Step: 1
First of all, you need to install support for Windows complex script to view complex Asian characters like Bangla.
You can download it from here http://www.omicronlab.com/go.php?id=38
(alt) http://www.omicronlab.com/download/tools/iComplex_2.0.0.exe
Run it and install.
Step: 2
Install an Unicode Bangla font. You can download a nice Bangla font from here http://arup.kamal.googlepages.com/BNG.ttf
Download it and copy that file into Control Panel > Fonts. After copying the font press F5 twice. It will refresh the font list Window.
Step 3
Configure you browser so that it uses your newly installed Bangla unicode font.
1. For Internet Explorer user, go to Tools > Internet Options. Click on the Fonts button. Then select Language Script : Bengali, Webpage font: BNG. Click Ok.
2. For Firefox user, go to Tool > Options. Then go to Contents tab. Click on the Advanced under Fonts and Colors option. Select Fonts for Bengali, and select BNG

How to write Bangla in WordPress
Install Avro http://www.omicronlab.com/go.php?id=36 (alt) http://www.omicronlab.com/avro-keyboard-download.html or Avro Portable http://www.omicronlab.com/go.php?id=37 (alt) http://www.omicronlab.com/portable-avro-keyboard.html to write Bangla in WordPress or anywhere in web. After installing it please read the help file.