Step 1: Download the ZIP of CyanogenMod 7.1 RC1 from here. Each of the 69 supported devices has a separate ZIP, so be sure to confirm your device’s name first and then download the right file. Flashing the wrong file can have disastrous consequences.
Step 2: Transfer the ZIP to directly under /sdcard on your device.
Step 3: Turn off your device.
Step 4: Now, by pressing and holding a specific combination of buttons, you must boot into ClockworkMod (CWM) Recovery. This combination is different for different devices, so search for your device’s combination on Google.
Step 5: After entering CWM, take a nandroid backup. This will come handy later on if you wish to revert to your earlier set-up.
Step 6: From main menu, select wipe data / factory reset. This will wipe all personal data from your device.
Similarly, select wipe cache and wipe Dalvik cache from under advanced menu.
Step 7: From main menu, navigate to install zip from sdcard > choose zip from sdcard and select the file you transferred to /sdcard in Step 1.
Step 8: After flashing, simply select reboot system now from main menu.
