Help how do you have friends unlock level?
First you have to send out the requests by clicking on 'Ask Friends For Help' then another window should pop up prompting you to choose which of your friends you'd want to send the requests to. After choosing who to send it to, just hit 'Send'. Make sure that you choose 'Confirm' (or 'Okay', not sure) on the next pop up window for confirmation.
There are two ways that I know of for your friends to accept you request and unlock the level, (1) if they have the Candy Crush app installed, they just need to wait until the app has fully sync; (2) or, if they are using a laptop/desktop and is logged in on Facebook, they should see a notification for your request. They just need to click it, then wait for Candy Crush to load.
Either way they should get a mail on the top left corner of their screen. Click it then select the request you sent and then 'Confirm'. That's it.
PS. It's better to send ticket/life requests to those already plays Candy Crush or to those you're really close with who won't mind the frequent requests.