The last time American astronauts were launched to the International Space Station from U.S. soil was in 2011. Since then, we have relied on launches from Russian soil. NASA and SpaceX are targeting 4:33 p.m. EDT Wednesday, May 27, for the launch from Florida of a two astronaut crew to the ISS. Crew Dragon Demo-2 is scheduled to dock to the ISS at 11:29 a.m. Thursday, May 28. More details of the timeline are here. Check NASA-TV for coverage. A successful flight of the unmanned Crew Dragon Demo-1 to the ISS was conducted in March 2020.
A critical part of the mission is docking Dragon to the ISS. Spaceflight is complex. To be in low Earth orbit, spacecraft need to travel 5 mi/s (8 km/s) to avoid falling closer to Earth. To approach and dock to another spacecraft as in this mission, their relative motions as they near must be very slow and precise while still going extremely fast. It is much like a flight attendant carefully handing you a drink while the plane flies 500 mph. No sudden moves.
There are 6 degrees of freedom of motion in space including 3 translational and 3 rotational. Translation includes movement and speed forward or back, up or down, and right or left. Rotation includes movement and speed called roll which rotates clockwise or counterclockwise while looking forward, yaw points the nose left or right, and pitch points the nose up or down.
The astronauts will use a digital interface to control the 6 motions of the Dragon. This brief video gives a view of its appearance as they use a simulator to practice their approach. It allows the astronauts to control rotations and translations as they approach ISS and get into position for a secure docking latch.
They must insert the nose of the Crew Dragon securely into this round opening which is attached to the ISS. Docking allows an airtight seal and doorway into the ISS. For a sense of scale, an astronaut is servicing the docking collar in 2016.
You can use this simulator yourself to feel the challenges they will experience. Click the Instructions button and find 7 important explanations. It is easy to go too fast or far, then over-compensate trying to correct. No one will get hurt by your play. Give it a try. Post successes or failures in comments.