I made a guide thread when i got out of bronze for the first time few weaks ago. It's actually easy, but you are the one who must lead your team to victory. You can never hope for all of 4 of them to win for you.
Those are the champions i recommend in bronze

Don't die, don't throw, focus on split pushing. In laning phase, don't miss a last hit. doing this will make you farm a lot which will make you become rich enough to take the lead. Split pushing is also good to take down enemy towers and to make sure your own towers don't get taken down.
If you wish to participate in team fights, don't stand around in a stagnated moment. Join the team fight to wipe the enemy quick. If the fight becomes stagnate, go hop on a lane and push it all the way. Get ready to escape in case an enemy is following you.
Most importantly, ward a lot, ward for your team, communicate. Buying pink ward everytime to place it in the single bush is always a good idea.