1. On your main sawmill, you may receive a task that asks you to evolve a machine.
To evolve it, you need a manager with a high enough level.

2. Manager level increases when you use manager cards.
The task will show which manager level you need for the evolution.

3. Once your manager reaches the required level, the “Evolve” button becomes active and you can complete the task.

The requirements always show which level of manager you need.

Once you have enough cards, the "Evolve" button will become active.