how might i be able to use a permutation and combination formula with this online calculator?

I guess

if you want    6C3  for instance you would type

nCr(6,3)

and this is the output   :)

$${\left({\frac{{\mathtt{6}}{!}}{{\mathtt{3}}{!}{\mathtt{\,\times\,}}({\mathtt{6}}{\mathtt{\,-\,}}{\mathtt{3}}){!}}}\right)} = {\mathtt{20}}$$

You can also use the function "binom(6,3)"

and the output is

$${\left({\frac{{\mathtt{6}}{!}}{{\mathtt{3}}{!}{\mathtt{\,\times\,}}({\mathtt{6}}{\mathtt{\,-\,}}{\mathtt{3}}){!}}}\right)} = {\mathtt{20}}$$