I created Bitcoin private and public key pair for Bitcoin. I am looking a way to receive funds to my Bitcoin address. The wallet apps which support buying or selling bitcoins are generating bitcoin addresses again. How can I buy bitcoins to my own account instead of wallet generated addresses?
I suppose you are using an HD wallet which all modern wallet apps use, the fact that a new address is created for you each time you want to receive bitcoin is in fact designed to improve privacy and security.
All of the address generated by your wallet which is called an HD wallet are derived from a seed and you are supposed to have a "Mnemonic phrase" (a list of words) which kind of act as your private key and must have been generated at the creation of your wallet.
You can still access the individual private key of each address, keep in mind that exposing them is not secure see @Chris Chen comment the procedure depend on each wallet software, accessing those are usually not necessary.
Here is more information about HD wallet and Mnemonic phrase
1Manually exporting individual private keys brings potential risk that all the child private keys can be inferred with the parent xpub combined with any individual child private key, so that leaking any inidividual child private key can be risky. Hardened derivation of addresses eliminates such risk, as well as the main advantage of HD wallet, that new addresses could be generated/derived without any private key. May 11, 2020 at 1:43
Despite such weakness of HD wallet, I still strongly prefer it rather than directly using individual private keys. Exporting reused non-HD-derivated individual private keys brings similar risk, which should be avoided by not carelessly exporting privkeys anyway. BIP44/49/84 also provides isolation against such risk by using "accounts" (where the account extended keypair themselves, aka. xpub/xprv/ypub/yprv/zpub/zprv etc, are hardened-derivated), so that even a breach of one account won't affect other accounts. May 11, 2020 at 5:18
1"linked internally by a seed" - shouldn't be "derived from a seed"? I agree that the derivation itself could be considered a linkage, however, such linkage isn't visible in any way, unless with the knowledge of extended public or private key or the mnemonic phrase itself. May 11, 2020 at 5:28