Update README.md

README.md

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 # google-drive-ResumableUpload
 A helpful java library/class for uploading large files in chunks on google drive.
+
+## Example usage for uploading a file
+
+Here's an example for uploading a java.io.File to google drive.
+
+```java
+// Make sure we've already got Google OAuth Credentials object `credential` and
+// java.io.File object `file` for the desired file to be uploaded.
+
+// Now create the metadata google drive file with the name, mime-type and size
+File fmeta = new File();
+fmeta.setName("My Report");
+fmeta.setMimeType("application/vnd.google-apps.spreadsheet");
+fmeta.setSize(file.length()); // `file` is the object for the desired java.io.File
+
+// Now, use uploadFile() method to start uploading the file in multi-part requests.
+ResumableUpload.uploadFile(credential, fmeta, file);
+```
+## How this works
+
+ - At, first we use the `requestUploadUrl()` to create a new request to the google drive api for
+our requirement of uploading a file. This method returns the url retured by the google api, which we'll be
+using to upload the file data.
+ - Then we can use `uploadFilePacket()` to upload a part of a file or `uploadStringPacket()` to upload
+ a part of any string as a file data. This step can repeated for each part of part of the file.
+