More details of the mission can be found here:

https://science.nasa.gov/mission/nisar

https://www.isro.gov.in/Mission_GSLVF16_NISAR_Home.html

https://nisar.jpl.nasa.gov

Press release about the launch: https://www.nasa.gov/news-release/nasa-sets-launch-coverage-for-earth-tracking-nisar-satellite

*Videos*:

As per this video, satellite data will be freely available: https://www.youtube.com/watch?v=wwfvKO9LUnA

Promos and short explainers:

https://www.youtube.com/watch?v=2AFEbG16mY4

https://www.youtube.com/watch?v=zM_0aXxGN6g

https://www.youtube.com/watch?v=SjdwdVKK11Y

https://www.youtube.com/watch?v=LJLraRzWVh8

https://www.youtube.com/watch?v=IX6lL0c4vEg

https://www.youtube.com/watch?v=RclF5xRSuJA

Detailed explainers:

https://www.youtube.com/watch?v=lKOZyv0Ux-k

https://www.youtube.com/watch?v=JVDDcUNi_mo

https://www.youtube.com/watch?v=fmGr5rT_QEQ

https://www.youtube.com/watch?v=mWuxfecV3l8

https://www.youtube.com/watch?v=EtVlA0-ykO8

Prelaunch news conference: https://www.youtube.com/watch?v=qEjqjv3Li8A

Live streaming links:

https://www.isro.gov.in/GSLVF16_NISAR_LiveStreaming.html

NASA's YouTube channel: https://www.youtube.com/watch?v=waTmU9hyOqo

NASA's streaming platform: https://plus.nasa.gov/scheduled-video/nisar-launch

https://www.nasa.gov/ways-to-watch

HTH