You can do it very easily.. That's the beauty of steemit. Nothing is ever too hard
So now to come to what you have to do-
-Log Into your account.
-Go to your wallet.
-On the right side of "steem" it shows the amount you have. Tap/click on it and it will open a menu.
-Select power up option from there.
-Input the amount you want to use from what you have.
-Confirm transfer to vesting.
-Input your active/owner/master password if its asked to.
-click sign in.
And viola. you have successfully transferred steem to steem power aka vesting.
Thank you!