how do i use the -1 for sin

You don't - you use asin (press the 2nd button  to see it).

If I type asin(0.5), say into the Math Input here, you see sin^-1(0.5):

$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{sin}}^{\!\!\mathtt{-1}}{\left({\mathtt{0.5}}\right)} = {\mathtt{30^{\circ}}}$$

You type -1 in then press sin on the far right top corner of the calculator then press enter