JWT private key and public key - spring

Question

I have asked to create a JWT token for an API. For this I have use the jose4j dependency to generate and consume that token. I've given an example token that I've debbuged in jwt.io and it seems that I need a public and private key, as you can see in the signature below:
What I've done so far is this, following the documentation in jose4j bitbucket page:
public String createJWT() throws JoseException, MalformedClaimException {
RsaJsonWebKey rsaJsonWebKey = RsaJwkGenerator.generateJwk(2048);;
rsaJsonWebKey.setKeyId(keyId);
JwtClaims claims = new JwtClaims();
claims.setJwtId(keyId);
claims.setIssuer(issuer); // who creates the token and signs it
claims.setAudience(audience); // to whom the token is intended to be sent
claims.setSubject(subject); // the subject/principal is whom the token is about
claims.setExpirationTimeMinutesInTheFuture(60); // time when the token will expire (10 minutes from now)
claims.setGeneratedJwtId(); // a unique identifier for the token
claims.setIssuedAtToNow(); // when the token was issued/created (now)
claims.setNotBeforeMinutesInThePast(2); // time before which the token is not yet valid (2 minutes ago)
// A JWT is a JWS and/or a JWE with JSON claims as the payload.
// In this example it is a JWS so we create a JsonWebSignature object.
JsonWebSignature jws = new JsonWebSignature();
// The payload of the JWS is JSON content of the JWT Claims
jws.setPayload(claims.toJson());
// The JWT is signed using the private key
jws.setKey(rsaJsonWebKey.getPrivateKey());
The thing is I don't know from where I'm suppose to get this private key, or what should it be.
I have also a keydata class with a username and a password, are those attributes my private key?
Then I have the consumer like this:
JwtConsumer jwtConsumer = new JwtConsumerBuilder()
.setRequireExpirationTime() // the JWT must have an expiration time
.setAllowedClockSkewInSeconds(30) // allow some leeway in validating time based claims to account for clock skew
.setRequireSubject() // the JWT must have a subject claim
.setExpectedIssuer("Issuer") // whom the JWT needs to have been issued by
.setExpectedAudience("Audience") // to whom the JWT is intended for
.setVerificationKey(rsaJsonWebKey.getKey())// verify the signature with the public key
.setJwsAlgorithmConstraints( // only allow the expected signature algorithm(s) in the given context
AlgorithmConstraints.ConstraintType.PERMIT, AlgorithmIdentifiers.RSA_USING_SHA256) // which is only RS256 here
.build(); // create the JwtConsumer instance
Where in this line: .setVerificationKey(rsaJsonWebKey.getKey())// verify the signature with the public key the code supponse to retrieve the public key.
So from where I'm suppose to get those key? Should I ask my collegues for them or what?