Designers with the appropriate permissions can change the characteristics of a Stream:

1. Go to Gear Menu > Streams Management
2. Click on the Stream you want to inspect or modify

To make small changes, you can unlock the ​stream. (Typically, that is something you do only to unblock records that are In Error.) When you lock the stream once again, your modifications are immediately available to all records that are currently using that version of the process.

 

For more substantial changes, you will checkout the stream. When you are done making your modifications, you will checkin the stream, which allows others to make changes.

 

When you are done making changes, you will publish the working version, which places it into general use. New records will use the new version, while records that are currently in progress continue using the old version. (You can publish a stream definition only if you have the appropriate permissions.)

 

Learn more: Checkout, Checkin, Publishing, Versions