First of all download BOMBUS
on your mobile and than follow the following steps..
1~ open bombus application
2~ press option and select new account
3~ user name = your nimbuzz id
4~ password = your nimbuzz id password
5~ server = nimbuzz.com
6~ host name/ip = Openfire.nimbuzz.com
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7~ port = 5222
8~ no compression
9~ keep-alive = 1byte
10~ keep-alive period = 400
11~ resource = bombus+
12~ nickname = as u wish
13~ and than press option and select "ok"