Dears,

i have exchange server 2013 so i need to configure high availability, so can you please guide us

You really need to have some understanding in how the concept of High Availability for Exchange before you start deploying it.  I would suggest you first take a look at the links below.

http://exchangeserverpro.com/exchange-server-high-availability/

http://exchangeserverpro.com/exchange-2013-client-access-server-high-availability/

http://exchangeserverpro.com/exchange-server-2013-database-availability-groups/

https://technet.microsoft.com/en-us/library/dd638129%28v=exchg.150%29.aspx?f=255&MSPPError=-2147217396

https://technet.microsoft.com/en-us/library/dd638137(v=exchg.150).aspx