Q: recieved this msg on my phone: to contiune using icloud on this iphone approve it from one of your other devices using icloud or enter your icloud secuity code. (wait time 2 days) is this legit? how do i do this?

I'M not sure, it could be...

If you enter your iCloud Security Code incorrectly too many times - Apple Support

The question I have is - how do I approve it from one of my other devices using iCloud?

How did you receive it? Text message?

If it was a text message I would leave it alone.

If it was a notification or a setting on the phone it is legit, you don't have to do it but you can if you like your passwords synced on every apple device you own.

For info on setting it up follow this link

http://www.macworld.com/article/2058081/how-to-use-icloud-keychain.html

I didn't find the settings on my Mac that matched those instructions.   But it told me enough that I learned that I should turn off key chain on my phone and pad.   That will get rid of the irritating pop-up.   It's not obvious to me what I lose from doing so, but I could find no other way to get rid of the pop-up.