how do i add

in the calculator: press a number, the + sign, and then the number you want to add to the first number. then hit enter.

in real life:

all you need to know is the digits:
0 1 2 3 4 5 6 7 8 9 in that order.
1 is the unit, the most important part. (addition is just repeated units). 2 equals 1 and 1, 3 equals 1 and 1 and 1, 4 equals 1 and 1 and 1 and 1, and it continues in that pattern. remember this, its also important.
0 is equal to having no 1s.

when you add 1 and 1, you get 2. but what if you add 2 and 1?

well, 2 just equals 1 and 1, so adding 2 and 1 is the same as adding 1 and 1 and 1.
1 and 1 and 1 equals 3, so 2 added to 1 equals 3.

it is more commonly known as "plus" or "+"
for example, "1 plus 1 is 2" or "1 + 1 is 2"

once you reach 0 (1 1 1 1 1 1 1 1 1), you may wonder

Whats nine plus one?
when you get to nine, the next number is just 0 again.
however, you add 1 to the left of it.
9 + 1 is 10
10 + 1 is 11
11 + 1 is 12... and it continues to 19.

19 + 1 is 20.
29 + 1 is 30.

and it continues on
99 + 1 is 100.
100 + 1 is 101.

of course there are numbers in between and beyond those ones but im sure you understand that i dont have
time to list every number, which there are an endless supply of.

hopefully this helps.
Happy adding!