Where do I start in Salesforce?

Mysql Data Masking tool is basically designed to secure sensitive information from unauthorized user.
for more information please visit here:-

https://www.datasunrise.com/masking/mysql/

Welcome buddy!

You can check on Trialhead, plus do let me know if you need any more help in understanding the things on it as you are fairly new.

Regards,

Shekhar

Please check out : Trailhead.com

start in Trailhead. Free tool, gives both theory and hands on experience. You can select what you are interested in. You can have up to 10 orgs against your Trailhead account, but if you don't want to use one anymore or make a mess, just remove it and create a new one. Endless possibilities to mess around in the system
However, make sure you also focus on how the system works, so do the Administrator Trailmix. You can be the most fantastic coding expert in the world, but if you don't know the options and limitations of Salesforce as well as a very good understanding how End Users use the system, you won't get very far.