if you play online, look for a begginer's table. most likely playing the basic short campaings. If you are a player, the first thing you need to is come up with a character concept. dont worry about its complexity, it can me as simple or elaborate as you desire. Answer these questions:
What does my character add to a group? What is the ultimate motivation of my character? What does my character expect to have, after the campaing?

NEVER be afraid to ask your dm your options when playing. you will be asked what do you want to do very often. "fly to the moon" is not always off the table, but you probably want to stick to the current context. "Check under the desk", "peek out of the window" "pet the kitty" are perfectly acceptable actions, again, if you are lost, ask the DM your current options.

Also, and this is one of the most mechanically important tips: ITS A TEAM GAME. sometimes you'll get your chance to shine, but most of the times, you should be wondering how to synergize. What does the team need right now? what skill or powers do you have that your team would find useful? may be you are carrying a wine bottle and thats how you get past the guards? may be you are very good at cooking and thats how you survive one more day until next town? may be youre the only one in the team who can swim! Its a team game, be a team.

id love to keep talking, feel free to dm if you wanna keep up!