If I have a reductive algebraic group $G$ defined over a non-archimedean local field $F$. We can define a one-parameter subgroup to be a group homomorphism from $G_{m}$ to $G$. I was wondering, if I have a reductive algebraic group $G$ is there a set of steps that one can follow to find the set of one parameter subgroups of $G$.
Or in general, what are good references to read about this?