From your Rise Client desktop wallet, under the "My Accounts" window click on your Rise address (highlighted in the picture below).
This will bring up the Address window. From here you can view transactions, send Rise or vote for a delegate.
Click on the "VOTES" tab.
When you click on the "VOTES" tab, you will see this list. You have to physically add a delegate before you can choose which one to vote for.
Click on the green "ADD DELEGATE" box.
Clicking on "ADD DELEGATE" brings up an Add Delegate entry box.
You can view a list of delegate proposals on the Rise forums at https://forum.rise.vision/category/5/delegates-proposals
Be sure to read the proposals because some of them are private and require you to contact the delegate. Some of them also have minimum limits on the amount of Rise you have in your wallet.
For my delegate I typed in the delegate name doom and clicked "ADD DELEGATE"
After you add your delegate make sure you click the box next to the delegate's name. There should be a check mark in the box of the delegate you want to vote for.
Click the red "VOTE" box.
An entry box pops up showing that I am adding the delegate doom (+doom) and asks me for my passphrase. Enter your passphrase and click "NEXT"
Note: the same box pops up when you want to remove the vote for your delegate with a minus sign (-doom)
A transaction box pops up after you enter your passphrase asking you to confirm the transaction. It only costs 1RISE to vote for a delegate.
Confirm your vote by clicking "SEND R1 NOW!"
You're good to go. You will start receiving your share within a few days depending on the delegate you have chosen. The amount of shared rewards you get is dependent on the amount of RISE in your wallet. You can add or remove RISE at any time and don't have to change or update anything, it is automatic.
You also do not have to be online with your wallet open like normal Proof of Stake. Your delegate is staking for you.
If you have any problems or questions join the Slack channel. Go to http://slack.rise.vision/ for an invite. There are plenty of people there willing to help.