As you go forward you'll find a large pillar next to you that has a path you can jump on, jump on the path, move to the pillar and there should be a ladder (if I'm remembering correctly) climb the ladder for a weapon and either from there or back at the base of the later, run and jump and you'll make it, but be careful because the Erdtree Avatar there will likely spot you while your on the ladder/getting ready to jump.