Investments work on a structure that you have an Investment account and then you have the securities you own in the investment account. Some equate an investment account to a brokerage account and the securities to the shares you have purchased through this broker. But this is completely arbitary, for example you may setup each company you own shares in as an Investment account and the shares as the security.
So you need to create a security for the Investment you have and add it to the Investment account. Purchases and sale of the investment is made against the security and any dividends are also against the security. Think of the Investment account as just being the container that holds the investment, not the investment itself.
The knowledge base articles may help you with background and also how to do things.