To use the blockchain you need a private key which is calculated from your Mnemonic Phrase. This Mnemonic Phrase is the key to everything. It is important that you make sure to keep it safe and secret.
In case you are operating your own node you can use the server based key management functions as explained HERE.
If you do not operate your own node kindly use the the client based generator below:
If you do not have a Mnemonic Phrase yet you can generate one on: