There's a few things you can do. You can offer to help them by saying "Hey teammate, I have an idea that might make laning easier on you. Do you want to know what it is?" People are more receptive to your advice when you word it this way. They have the opportunity to decline your help or accept it. If they accept it then give your idea. If they decline it stay for a little bit and watch to see if they improve. They typically don't.
After trying the above strategy you're free to do any of the following. Ask your jungler if they want a ward placed anywhere specific in the enemy jungle. Ward dragon so your team is able to make a steal or take top lane tower in retaliation. Ward your own jungle in order to prevent counter jungling. Gank mid lane. Help with an invade.
Just communicate what you're planning on doing. Your ADC will get pissed most likely but your other teammates will appreciate your willingness to help them out.