You add decimals by just adding it but you have to put the decimal.
ex: 1.25
+2.13
=3.38
Some things you have to remember are...
*Keep it right under each other if you want to keep your work neat!
ex: 1.25 1.25
+2.13 +2.13
3.38 right 3.38 wrong

* You always start with the hundreths spot! ex: 1.25 start here and go down
+2.13
=3.38

It is important to learn about decimals so that when you go to the store you can add to items together.
ex: apple-1.24
chips-3.34 1.24
+3.34
=4.58