There are tutorials explaining how to flash ROMs all over the internet, but here are the steps:
1. Root your device
2. Flash TWRP recovery
3. Download the latest CM build & GApps and save them to the root of your SD
4. Boot into recovery
5. Make a backup of your current ROM just in case something goes wrong
6. Wipe cache/dalvik, boot, system, and data
7.Install CM and GApps from zip
8. If all goes well and right, you should be able to reboot into CM
There's a tutorial for rooting and flashing TWRP recovery to the Stylo posted on the XDA developer forums. Do some googling, it should come right up.