1. In OBS click Settings in the bottom right hand corner. 
2. In the Settings window click Stream. 
3. In the Stream section, select from the Service dropdown menu where you would like to stream to.
4. Follow the instructions of your selected streaming platform (including acquiring a stream key) and paste the stream key into the Stream Key box. 
5. Click Apply to close the Settings window and return to the main OBS window.
6. When you are ready to stream from OBS select Start Streaming in the bottom right hand corner. 

4K Streaming

1. In Settings go to Output and for Output Mode select 'Advanced'
   1. Under Encoder selectNVEnc
   2. Under Rate Control select CBR
   3. Set the Bit Rate to at least 30000 Kbs - (ie 30Mbs).
   4. Ensure that the Keyframe Interval is not 0. (4 seems to be a good interval for YouTube.) 

Minimum Internet Upload Speeds

1. You should increase the Bitrate as explained above to minimize compression for higher resolution outputs.