First, familiarize yourself with the data structure in Opsgenie. Identify the specific data you need to transfer, such as alerts, incidents, or any other relevant information. Use Opsgenie's API documentation to understand the endpoints you'll interact with and the data types involved.

To extract data from Opsgenie, you'll need to set up API access. Generate an API key by navigating to the Opsgenie settings, and under the API section, create a key with the necessary permissions to read the data you plan to transfer. Note down this API key securely.

Use the Opsgenie API to programmatically extract data. This can be done using a scripting language like Python. For example, use Python's `requests` library to make HTTP GET requests to the Opsgenie endpoints using your API key. Parse the JSON responses to retrieve the data you need.

```python
import requests

api_key = 'your_opsgenie_api_key'
headers = {
'Authorization': f'GenieKey {api_key}'
}
response = requests.get('https://api.opsgenie.com/v2/alerts', headers=headers)
data = response.json()
```

Next, transform the extracted data to fit the schema of your Weaviate instance. Ensure that the data types and structures align with the classes and properties defined in Weaviate. You may need to write a transformation script, possibly using Python, to reformat the data accordingly.

Ensure that your Weaviate instance is running and accessible. Configure the schema in Weaviate to accommodate the incoming data. This involves defining classes and properties that match the transformed data structure. Use Weaviate's REST API to create this schema if it hasn't been set up yet.

Utilize Weaviate's REST API to import the transformed data. This involves making HTTP POST requests to the Weaviate endpoint with the data payload. Ensure that each data entry is correctly formatted to match the Weaviate schema.

```python
for item in transformed_data:
response = requests.post('http://localhost:8080/v1/objects', json=item)
if response.status_code != 200:
print(f"Failed to import: {response.text}")
```

Finally, verify that the data has been successfully imported into Weaviate. Use Weaviate's query capabilities to check for data integrity and completeness. Compare the data in Weaviate with the original data in Opsgenie to ensure accuracy. Make necessary adjustments if there are discrepancies.

By following these steps, you can efficiently move data from Opsgenie to Weaviate without relying on third-party connectors or integrations.