Ok, in your wallet you will see there is steem and steempower, you get steem from voting, and from posting or commenting then if people vote you obviously get steem. I will skip the whole 50/50 thing for now :) Now steempower is that steem but invested for longterm which gives you vests (stake) the more stake you have the larger your vote and with the latest hardfork the more bandwidth or as they now call it resource credits you have, this allows you not to just have a bigger vote but also do more on the blockchain , you can see how much you can do here (a note watch that percentage bar that is your resources for 5 days - ideally you never really want to go below 80% - it replenishes 20% every 24hours) https://steemd.com/@lulabelle

Ok, sorry that was a lot of unrelated but related content.

You power up in your wallet, when you select steem which is liquid (it can be spent) you will get the option to transfer or powerup (you want powerup) , this will move it to steempower which increases the account value on the platform
.

You will need to copy your active key to do this , and I sincerely hope you are only using your posting key to post etc.

Please review these for more info on the keys you need to keep safe - this guide is for steem in general but for the keys please read and understand this https://steemit.com/steem-help/@sykochica/answering-common-questions-what-are-all-these-keys-in-my-wallet-why-so-many and this https://steemit.com/steemit/@ethandsmith/the-beginner-s-guide-to-steemit-part-2-logging-in-and-keeping-your-account-safe