How do I add my securities to my Investments account?

If you haven't held shares of your security for too long, or if you have very few transactions (e.g. you purchased shares of the security twice, back in 2014 and again in 2017), you can enter the actual transactions on the dates you made them. Normally, this would be done with a Buy transaction — but a Buy transaction will decrease the cash in your account to reflect the purchase. While this is fine going forward, it may not be for the past, because you'd also need to enter the transactions which moved cash into your brokerage account. So in this case, you can enter an Add Shares transaction, which allows you to specify the date and number of shares acquired on that date, but it won't decrease cash in the account. 

To enter a transaction, click on the account in the left sidebar, click on the Transactions tab, enter the Date, and in the Type field, select Add Shares from the dropdown menu. 

If you have a lot of transaction or long account history you don't wish to re-create in Quicken, you can simply do one Add Shares transaction to create the number of shares as of a particular date. in this case, you likely won't know what amount you paid for the cumulative shares, so you'll just have to enter a guesstimate, or use the average cost if your brokerage provides that information. (In this case, Quicken won't be able to provide you precise gains calculations for tax purposes in the future, because it doesn't know the exact purchase price of all your shares; rely on your brokerage statement or 1099 for the correct data for your taxes.)

If you want to be able to see your transactions going forward, make sure the account in Quicken is set to Detailed tracking; if it is set to Simple tracking, you'll only see your account balance being updated, but not the actual transactions which take place.

If anything isn't clear, post back with more questions.