The Briton, 33, looks for his first win since 2020 after successive defeats by unified champion Oleksandr Usyk.
Joshua said he was more serious than ever before about his boxing career.
"I've always tried to make an empire but I made a conscious decision last year to put my heart into boxing and nothing else," he said.
"Throughout my career, this is probably the most serious time I've taken it."
Joshua was joined by his new coach Derrick James, with both men flying from Texas to London to attend the news conference.