The key to beginning any foreign language is learning enough essential vocabulary to use in conversation. Many of the first words and phrases that you learn will involve greetings as well as basic vocabulary for everyday items. Such phrases in Portuguese include "Bom dia" (good morning) or "Ate logo" (see you later). Memorize these words and phrases by going over them on a daily basis. Make flash cards and review essential vocabulary by testing yourself on the meaning and pronunciation of words.
Memorizing vocabulary will only get you so far. You must also be able to understand these words when they are spoken in Portuguese. Purchase a course with an audio component so you can get used to hearing the language spoken. Many courses come with audio CDs that have recorded conversations between native speakers. Listen to these conversations repeatedly until you can comprehend them naturally. Such audio courses also have question and answer formats where the recorded voice asks you a question and you respond. Practice answering as if you were responding to a native speaker.
After learning enough vocabulary and listening skills, the next step is to practice your Portuguese with a native speaker. Find someone who knows Portuguese fluently and is willing to help you. Often, native speakers will be thrilled that someone is taking the time to learn Portuguese and are rather understanding of mistakes. Don't be afraid to ask the person to repeat a word or phrase if you do not understand. After some practice, you will become comfortable enough speaking Portuguese to learn more advanced vocabulary and phrases.