In order to add a step in a running procedure you must be participating in the procedure AND an Admin or Editor.
Toggle "Participating" to on if it is not already.
Navigate to the step you would like to be before the newly added step.
Click the 3 dot menu and select + ADD STEP BELOW.
Enter a Name for the step.
Click + Add Content to add content to the step.
Scroll through the list and select the type of content block(s) you would like to add.
For additional content blocks hover over and click the + icon next to whatever block you want the next block to be below.
The content blocks can be duplicated or removed from this menu as well.
Tip!
You can quickly remove content blocks by clicking them and hitting the delete key on your keyboard.
Once you have finished building the step click the Save button and determine if the step will be added as a Blueline (only applied to this run) or a Redline (added to this run and included in the next draft)
Read more about Redlines and Bluelines in this article: Suggest Edits While Running