I agree with virmaior's answer using disjunctive syllogism (DS). Here is how Kevin Klement's proof checker would format the proof using disjunctive syllogism:
Disjunctive syllogism is derived from disjunction elimination (vE). Here is a proof using the disjunction elimination illustrating the derivation for disjunctive syllogism from disjunction elimination given in forall x: Calgary Remix (page 137):
Note how this uses conjunction introduction of "R" with itself on line 9 and then conjunction elimination on line 10 to get "R" again. The rules of this proof checker eliminates the need for those steps.
Here is a third version of the proof:
The OP has the same first four lines and states: "I can't figure out where to take it from line 4." The above shows three ways to proceed and there may be more depending on the proof checker one uses.
P. D. Magnus, Tim Button with additions by J. Robert Loftis remixed and revised by Aaron Thomas-Bolduc, Richard Zach, forallx Calgary Remix: An Introduction to Formal Logic, Winter 2018. http://forallx.openlogicproject.org/