If you want to share a note you go inside the specific note, then you look for the following share button. The image below is for the iPhone, so just tap on the 3 dots. On the iPad just press the share button directly.
Then just pick the email app you use directly or just save the note as an "image" to your Photos. Then you can email it using your email app.
Another way to share notes is via Patient Referral. In this case, you can securely share encrypted notes to another doctor, just hit the Refer button and you can now send the patient profile and your chosen notes to the receiving doctor.