Changing between the STEEM asset types (STEEM, STEEM Power, and STEEM Backed Dollars) is accomplished via your SteemIt wallet page.
You can purchase STEEM assets using Bitcoin. If you want to convert other cryptocurrencies into STEEM assets, you should be able to accomplish this through Blocktrades too (although I have not tried it).
I found using Blocktrades to be extremely easy when diversifying STEEM into other cryptocurrencies.
I am very glad you liked this article.
Have a great weekend!
Steem on,
Mike