I read the message you linked to, and ironically, I believe the person who wrote it appears to be adding to the word of God...
The person appears to be saying we can do all of the following signs if we believe:
Mark 16:17-18 NKJV "And these signs will follow those who believe: In My name they will cast out demons; they will speak with new tongues; they will take up serpents; and if they drink anything deadly, it will by no means hurt them; they will lay hands on the sick, and they will recover."
I believe Jesus' words. But I also believe in keeping things in context. It is important to note that these signs only happen according to God's will. It's God's choice to use whomever He desires to do these things, not ours. And just because you cannot do all of these things, it doesn't mean you are not a believer or that you don't have the Holy Spirit in you, as some falsely say.
It's not about what we want to do, but about what God wills.