Use quotation marks (" ") around the words or phrases you want to emphasize. This helps guide the Synthetic Voice in shaping the emphasis of your sentence.
E.g.: Are "you ready" to take your creative production to the "next level"? Use the “AudioGO self-service creative production” to “easily” create compelling, attention-grabbing, and persuasive voiceovers “in seconds”, and launch audio campaigns “on time”, without headaches and logistical nightmares.