create R

if (!require(haven)) {
  install.packages("haven", dependencies = TRUE)
  require(haven)
}

## Loading required package: haven

if (!require(psych)) {
  install.packages("psych", dependencies = TRUE)
  require(psych)
}

## Loading required package: psych

dataset <- read_sav("https://osf.io/kd4ej/download")

#create dataframe with only relevant variables to work with
Extraversion <- data.frame (dataset$FFM_1, dataset$FFM_6, dataset$FFM_11, dataset$FFM_16, dataset$FFM_21, dataset$FFM_26, dataset$FFM_31, dataset$FFM_36)

#create list of 'keys'. The  numbers just refer to the order of the question in the data.frame() you just made. The most important thing is to mark the questions that should be reversed scored with a '-'. 
Extraversion.keys <-make.keys(Extraversion,list(Extraversion=c(1,-2,3,4,-5,6,-7,8)))

#score the scale
Extraversion.scales <- scoreItems (Extraversion.keys, Extraversion)

#save the scores
Extraversion.scores <- Extraversion.scales$scores

#print the cronbach alpha
Extraversion.scales$alpha

##       Extraversion
## alpha    0.8141661