Like most of the services, Amazon MemoryDB for Redis is fully integrated with Amazon VPC and always launches your cluster in a VPC. It means that you cannot access it from outside your VPC. While initially exploring these services (MSK, Elasticache for Redis, etc.), I usually followed the documentation that involved setting up EC2, SSH-ing into the instance, installing/copying stuff (language, runtime, code, client, etc.), and then tried things out.
Most often, the first step is the hardest, and it's important for developers to have the least amount of friction as possible to "get going." I looked for simpler ways and found AWS Cloud9 to be super useful. It was quick, predictable, and had a bunch of useful tooling readily available.