Ensure you have access to both ClickHouse and Google Firestore. Install necessary tools such as ClickHouse client for querying and Python or any programming language SDK that supports Firestore operations. Also, ensure your Google Cloud project is set up, and you have the necessary authentication credentials for Firestore access.

Use the ClickHouse client or a script to query and extract the desired data. You can execute a SELECT statement to retrieve the data you need. Export this data into a common format like CSV or JSON which can be easily processed later. For example, use:
```shell
clickhouse-client --query="SELECT * FROM your_table" --format=JSON > data.json
```

Since Firestore is a NoSQL database, ensure that your data is structured in a key-value format. If your data is in CSV, convert it to JSON objects, as Firestore requires JSON-like structures. Each row in your data should map to a document in Firestore.

Install and configure the Firestore SDK for your preferred programming language. For Python, you can do this using:
```shell
pip install google-cloud-firestore
```
Authenticate your application using a service account key JSON file from your Google Cloud Console.

Write a script that reads the transformed data file and uploads each entry as a document in the Firestore collection. Ensure you handle any data typing issues and set appropriate document IDs or use Firestore's automatic ID generation.
```python
from google.cloud import firestore

db = firestore.Client()
collection_name = 'your_collection'

with open('data.json') as f:
data = json.load(f)
for item in data:
doc_ref = db.collection(collection_name).document() # or specify a document ID
doc_ref.set(item)
```

Run your script to upload the data to Firestore. Monitor the process for any errors or issues with data integrity. Ensure that all data is correctly uploaded by verifying a few entries in the Firestore console.

After the data load, verify the integrity of the data in Firestore by checking a sample of documents. Ensure all fields are correctly mapped. Once verified, clean up any local files or resources you no longer need, such as temporary data files or authentication keys (if they were copied to a different location).

By following this guide, you can manually transfer data from ClickHouse to Google Firestore while ensuring data integrity and compatibility.