Step 1 :

First go to Smartsteem site https://smartsteem.com?r=prince121.. Then you see a image like below . It is the dashboard of Smartsteem. Then click invest option.

Step 2 :

After clicking invest option , you will see a revenue calculator. Its a measurement of your vote. That calculate your vote value by your steem power (SP). After you enter get start option by click it .

Step 3 :

After clicking get start option , you will see vote selling option and get a screen like below : Then you need some step and follow them :

1. First enable your vote selling option
2. Click Authorize account option and Connect it by steemconnect.

Those are minimum option for selling your vote. If you want to sell your vote by fixed steem power vote only if voting power in higher option.