Okah was behind the October 1 attack as well as the bomb blast in Warri, Delta state, on March 15 both in 2010.
Sentenced alongside Okah was Obi Nwabueze. They were said to have planned the attacks with Henry, the elder brother of Charles, who is serving his own jail term in South Africa.
Henry was the leader of the Movement for the Emancipation of Niger Delta (MEND).
Delivering judgment on Wednesday, Gabriel Kolawole, a judge, held that the prosecution proved the charges preferred against Charles and Nwabueze beyond reasonable doubt.
In the 4 hour, 30 minutes judgment, Kolawole found the defendants guilty as charged.
The judge noted that the second defendant Nwabueze made himself available to run illegal errands for Henry who provided N1.2m used to purchase five fairly used cars deployed for the Warri blast while Charles provided N2m used for the purchase of the four cars deployed for the Independence Day blast in Abuja.
The court had earlier sentenced a third defendant, Edmund Ebiware, to life imprisonment on July 27, 2017, for his role also in the Abuja bomb blast.
Charles and Nwabueze, alongside Ebiware and Tiemkemfa Francis-Osvwo (aka General Gbokos) were first arraigned before the court on December 7, 2010 in connection with the bomb blasts.
But Francis-Osvwo later died in detention.