There are four different groups of players coming to the Combine, sorted by position group.
Day 1 arrival: offensive lineman, tight ends, special teams, place kicker
Day 2 arrival: quarterbacks, receivers, running backs
Day 3 arrival: defensive line, linebackers
Day 4 arrival: defensive backs
Each group will go through the same schedule, just staggered by which day they arrive.
Day 1 schedule: Travel to Indianapolis, registration, hospital pre-exam and x-rays, orientation, interviews
Day 2 schedule: Measurements, medical examinations, media, interviews*
*Raiders head coach Dennis Allen will address the media at 11:15 am Pacific time
Day 3 schedule: NFLPA meeting, psychological testing, PK/ST workout, bench press, interviews
Day 4 schedule: On-field workout (timing, stations, skill drills), departure from Indianapolis
Day 1 arrivals have completed their day 1 schedule and are moving onto the day 2 schedule on Thursday. Day 2 arrivals are starting their schedule on Thursday. Day 3 arrivals will be in Indy on Friday and Day 4 arrivals will come on Saturday, which means the Combine won't be over until next Tuesday.
On Thursday and Friday NFL Network will be providing press conference coverage at 11:00 a.m. Pacific Standard tim9e. The actual drills don't start until Saturday and NFL Network will be there to air those each day at 6:00 a.m. Pacific Standard time.
Via the NFL Network release: "Live coverage of on-field workouts begins Saturday, February 23 at 9:00 AM ET with the offensive linemen,tight ends and kickers, and continues with the running backs, quarterbacks and wide receivers on Sunday, February 24, linebackers and defensive linemen on Monday, February 25 and defensive backs on Tuesday, February 26. Coverage of workouts begins each day at 9:00 AM ET."
There are also position-specific drills, which you can read about here.
Enjoy the combine!