You didn't state what type of router you had, so I'm going to give you an example for, say, a 2800.
Assuming that you're not natting at all on the FW (from the diagram you shouldn't be), you can do something like the following on the dsl router:
ip nat inside source static 10.100.2.25 188.53.62.x
ip nat out
ip nat in
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Thanks for your reply brother.
I am having 1841 series router. And I want to configure my static nat at Firewall. My firewall is cisco 5520
static (inside,outside) 192.168.201.12 10.1.1.3 netmask 255.255.255.255
This command maps an inside IP address (10.1.1.3) to an outside IP address (192.168.201.12).