Begin by cloning the GitHub repository containing the data you want to move to your local machine. Open your terminal and use the `git clone` command followed by the repository URL. This will download the repository content, including any data files, to your local system.

```bash
git clone https://github.com/username/repository.git
```

Navigate to the cloned repository directory and identify the data files you need to transfer to Postgres. The data might be in formats like CSV, JSON, or SQL. Use tools like `ls` to list the files and determine the files' structure and format.

```bash
cd repository
ls
```

Open and inspect the data files using a text editor or command-line tools to ensure they are formatted correctly for import into Postgres. If the data requires cleaning or modification (e.g., removing headers or fixing delimiters), make these changes now using tools like `sed` or `awk`.

```bash
awk -F',' '{print $1, $2, $3}' data.csv > cleaned_data.csv
```

Ensure you have Postgres installed on your local machine or server. Create a new database if necessary using the `createdb` command. Access the Postgres shell with the `psql` command to execute SQL commands and manage your database.

```bash
createdb mydatabase
psql mydatabase
```

Based on the structure of the data files, create the necessary tables in your Postgres database. Use the `CREATE TABLE` SQL command to define the tables and their columns, ensuring the data types match the data you intend to import.

```sql
CREATE TABLE mytable (
id SERIAL PRIMARY KEY,
column1 VARCHAR(255),
column2 INTEGER,
column3 DATE
);
```

Use the `\copy` command within the `psql` shell to import data from the local files into the corresponding Postgres tables. This command is efficient for loading data from CSV or similar formatted files.

```sql
\copy mytable(column1, column2, column3) FROM 'cleaned_data.csv' DELIMITER ',' CSV HEADER;
```

After the data import, run basic queries in the Postgres shell to verify the data has been imported correctly. Use `SELECT` statements to check a few rows and ensure the data integrity is maintained.

```sql
SELECT FROM mytable LIMIT 10;
```

By following these steps, you can manually move data from a GitHub repository to a Postgres database without relying on third-party connectors or integrations.