For email between two Gmail accounts, you can just go to that “Accounts and Imports” tab and click the “Add POP3 email account” right under where it says “Get your mail from other accounts in Gmail using POP3” and put in the information there.
You may have to manually enable POP3 on the remote account, you can do that by just going to Settings -> “Forwarding and POP/IMAP” on it. But it seems like it’s enabled by default for me.
Just for the record, I have a few accounts that funnel into one. It generally takes about 30 minutes for me to receive an email from those remote accounts in my main inbox. From time to time, from certain people, I won’t get the email for a day or two for whatever reason. So make sure any highly important emails are sent directly to your main account.