One of the most beautiful spider plants I've ever seen! And that is saying something because in my day every hippie had a spider plant, even those in a store aren't as beautiful. Good job!
If you have just repotted this plant then this is easy. On the side you want the plant to move to be more vertical, simply press the soil down on that side. Help your plant by holding the base and all the leaves in one hand while the other presses down the soil. The soil in your pot should be firmed down anyway. When your plant is upright, then gently press the rest of the soil down in the pot. I've even pulled newly planted plants upward slightly to firm the soil down on the side it is leaning towards and shake and poke soil under the roots of the far side. In fact this is probably best if you weren't firming the soil while repotting. Plants are tough. This will not hurt your plant.
If you were to just firm all the soil, water, your plant would eventually straighten quite nicely as it grows toward the light. But I would simply slightly pull the plant (is that one plant or two?) upwards, shake it gently or poke to get the soil to fill the pocket on the side it is leaning to be filled with more soil, then firmed under your plant when it is in the position you want. If this is one plant (could easily be made into two but don't) simply grab the lower parts in two hands and upright into position. Get into the soil to fill soil into the pocket left (right side?)and firm that soil below the roots to ensure the position. What ever management practices you have been using continue. Very happy plant! Kudos!!