SDM (Security Device Manager) allows you to configure and manage your router via the use of a GUI. Please find the steps below :

1. Download the SDM-Vxx.zip file from Cisco's website.
2. Ensure that you have the sdmconfig*.cfg file within your routers flash for your version of router. You can confirm this by using the command `show flash`.
3. If it is not then copy it from the SDM zip file previously mentioned.
4. Run the setup.exe from the zip. You can either install the SDM software on the router, local machine or both. It is advised to install this locally for performance reasons.
5. Now run the following commands on your router.

router(config)# username [password] secret [password] privilege 15
router(config)# ip http server
router(config)# ip http secure-server
router(config)# no ip http server
router(config)# ip http authentication local

Issue

If you face issues with the SDM connection box not opening your webbrowser and appearing to not do anything it will most likely be down to your version of Java. You will need to ensure that you are running the Java version j2re-1.4.2_05. You can download it from here.