updating readme for S3 compatible object storage

README.md

@@ -86,6 +86,20 @@ done < bam_files.txt
 
 rm bam_files.txt
 ```
+## S3 compatible object storage
+
+If using S3 compatible object storage, you will need to pass additional options to `mosaic bam` and `mosaic vcf`.
+Both of these commands take in -e and -p params which are the S3 endpoint URL and S3 profile respectively.
+In order to use these options correctly, the AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY environment variables
+must be set and a file, ~/.s3cfg, must also exist. The .s3cfg file should be formatted as shown below:
+```
+[test_profile]
+access_key = ****
+secret_key = ****
+host_base = https://test.com/
+```
+
+In this case, the -e option would be `https://test.com/` and the -p option would be `test_profile`
 
 ## Dependencies