how to change the PC use in the dimplot and feature plot
You can choose which PC dims to plot by specifying the dims argument within the functions. To use PC-4 and PC-5,

DimPlot(object = pbmc_small, dims = c(4, 5), reduction = "pca")


and

FeaturePlot(object = pbmc_small, features = "Xist", dims = c(4, 5), reduction = "pca")




Seurat documentation is available here.