I saw a job listing for a driver that required an active TS/SCI Fullscope Polygraph Clearance. How do I start?

that ball rolling? Initially I just wanted to work a part time job as a semi truck driver to go along with my FT federal government job. I do not have a CDL but would be willing to pay for any training program that leads to that. I have a good driving record, professional background, drug-free, no criminal convictions. I am retired military, willing to go through a paperwork process to get a clearance that does not involve a great deal of money (beyond basic truck driver training). I work ten hour shifts as a federal employee but in a two week pay period I am off 6 days, sometimes two to five days in a row.