Install the package on all nodes and get a code call library(thePackageYouUse)on all nodes using the available commands, something like
clusterApply(cl, library(thePackageYouUse))
, parallel, R, - . , , help(clusterApply), boot :
clusterEvalQ(cl, {
library(boot)
cd4.rg <- function(data, mle) MASS::mvrnorm(nrow(data), mle$m, mle$v)
cd4.mle <- list(m = colMeans(cd4), v = var(cd4))
NULL
})