Go to 'Goals & OKRs' section. Click on "New goal".
Enter a name for the goal, like "Accelerate product development".

Tap on it - to make goal as OKR.
 
Set a deadline. Most often OKRs are set for a quarter.
Set the visibility options:
  • Public – public goals are visible to all employees in the company (it allows everyone to understand where the company is going and what progress is being made)
  • Private – only seen by participants of the goal.
On the edit page of OKR:

Select the type of goal:
  • Personal - goals that can be set for particular employees.
  • Team - goals that can be set for a specific business unit or product team. Head of Department goals are group goals.
  • Company - goals that can be set at the company-wide level, such as a new product launch, revenue growth, or hiring plan. For example, all CEO goals are company goals.
Select the goal's priority
  • Low
  • Medium
  • High 
Select team member, who will be responsible for this goal.
You also can add goal contributors - employees, who can help to achieve the goal.
Add Key Results

Swith the Metrics key results tab - on. Then click on the " + " to create key results.
Enter name of the key result.
Select the metric, using which you can track the key result's progression:
  • Percent
  • Number 
  • Currency 
  • Achievable (Fulfilled/Not fulfilled)
  • Custom (you can set your own measurement)
Select the type of progression for the key result:
  • Increasing (e.g., sales)
  • Decreasing (e.g., number of codebases without tests)
  • Maintaining (e.g., number of support calls)
Set the current value of metric and the target value you want to achieve.
Choose a team member in charge (It is optional, and only if you have participants in the OKR).
Select a deadline (It is optional, if you want to put intermediate deadlines in the OKR).
Tap to 'Save' the Key result.
Add more Key Results (it is recommended to have 3-5 Key Results per OKR)
Save the OKR.
An added goal appears in the OKR list in one of the sections, depending on the selected type.