The easiest way to delegate is through SteemConnect. I made that link for you, so you don't need to fill in the delegator or delegatee.

You will need to calculate the amount of vests you'll be delegating. Fortunately, there's simple way to do that too. Go to this Steem Vest calculator and type in the amount of Steem Power you wish to delegate. The calculator will convert that amount to vests. In the SteemConnect link I gave you above, replace "0.000000" with the vest amount you just calculated.

And that's it! You'll have to fill in your username and password, to broadcast the transaction. SteemConnect is a very trustworthy source that handles thousands of transactions on the Steem blockchain every day.