Data made available in a Requester Pays Amazon S3 bucket can still be accessed in all the normal ways. However, the requester needs to pass a flag at request time indicating they know they will be charged for the request and any data egress. More details on this concept can be found at https://docs.aws.amazon.com/AmazonS3/latest/dev/RequesterPaysBuckets.html
The request mechanism can vary slightly depending on how you access the data currently. Links to some common access mechanisms are below:
A full list of documentation for the various access mechanisms can be found at https://aws.amazon.com/tools/.