After helping people set up mining in the Slack channel #mining, I noticed there wasn't a super simple guide on:

How to set up CLI Wallet (to control your main account)

Step 1.

Ensure that in your config, you have specified the RPC endpoint:

rpc-endpoint = 127.0.0.1:8090 

If this doesn't work, you may need to launch via "steemd --rpc-endpoint"

Step 2.

Launch cli_wallet. The first thing you need to do is set a password, you do this by typing:

set_password PASSWORD

Replace PASSWORD with any (regular character) password you like; make it strong and keep it safe! Don't worry if it spits out null. The next thing it should say is "locked".

Step 3.

Unlock you wallet with the command:

unlock PASSWORD

using the password you set in step 2.

Step 4.

You now need to find your private owner and active keys from your steemit.com account. Check out 

https://steemit.com/@YOU/permissions

Replace YOU with your username! Now find your private owner and active keys. Remember, keep these safe, tell them to no one.

Now, in cli_wallet, that is unlocked, you can import them one at a time as follows:

import_key OWNERKEY

import_key ACTIVEKEY

Replacing each key with the one you found on the permissions page.

Step 5. 

That's it, you are done. Now you can type "help" to see the cool commands you can do! But they are not the focus of this simple guide.

Some things you can now do is 

list_my_accounts

to see your balance (and confirm its working!), and you can also 

vote_for_witness YOU THEM true true

Replacing YOU with your account name, and THEM with theirs. Remember, vote for people you believe in! Check out https://steemd.com/witnesses and click the persons URL to find out more about them.

Step 6.

What, step 6?
Oh right.

You closed CLI wallet, and started it up again. Now what?

Simply go back and do Step 3 to unlock, and you are good to go!

That's it!
Hope this helps!