1st You will use left click to click on the duck and get coins
once you have coins you can do 3 things
1 Buy rebirths that double your coins per click of the duck
2 Buy friends I know you don't have friends in real life so you can buy them in the game to get extra coins per duck click (or quack as they call it)
3 scenery this makes the game look better and gives you coins per x amount of seconds depending on which one you have

First buy rebirths when you can this will speed up your coins by an insane amount
Next AFK doing this will give you lots of coins (just make sure you have a scenery first)
And lastly some people could call this "cheating" but its up to you use an auto clicker this makes the game so so SO easy if you are doing this it kind of takes the fun out of the game but if you do you can use OP auto clicker it works great

anyway thanks for reading if I missed anything please tell me in the comments (and tell me if I should do one for duck simulator 2!)