How can I use own Key for this AES CBC encryption in C++?

Providing this Code, the key and iv are randomly generated, this way it's not possible to create e.g. 2 Functions to decrypt and encrypt with AES. How can I set own key and iv? Or even better, how to "save" the randomly generated key's and use them for decryption afterwards?

string plain = text;
string cipher, encoded, recovered;

byte aeskey[AES::DEFAULT_KEYLENGTH]; 
byte iv[AES::BLOCKSIZE];


prng.GenerateBlock(aeskey, sizeof(aeskey)); 
prng.GenerateBlock(iv, sizeof(iv));



encoded.clear();
StringSource(aeskey, sizeof(aeskey), true, new HexEncoder(new StringSink(encoded))); 

encoded.clear();
StringSource(iv, sizeof(iv), true, new HexEncoder(new StringSink(encoded))); 




    try
    {
        cout << "plain text: " << plain << endl;

        CBC_Mode< AES >::Encryption Encrypt;
        Encrypt.SetKeyWithIV(aeskey, sizeof(aeskey), iv);
        StringSource s(plain, true, new StreamTransformationFilter(Encrypt, new StringSink(cipher)));

    }
    catch (const CryptoPP::Exception & Encrypt)
    {
        cerr << Encrypt.what() << endl;
        //exit(1);
    }

    encoded.clear();

    StringSource(cipher, true, new HexEncoder(new StringSink(encoded))); 
    cout << "cipher text: " << encoded << endl;







    try
    {
        std::cout << "HI" << "\n";

        CBC_Mode< AES >::Decryption Decrypt;
        Decrypt.SetKeyWithIV(aeskey, sizeof(aeskey), iv);

        StringSource c(cipher, true, new StreamTransformationFilter(Decrypt, new StringSink(recovered)));
        cout << "recovered text: " << recovered << endl;

    }
    catch (const CryptoPP::Exception & e)
    {
        cerr << e.what() << endl;
        exit(1);
    }