Here is an example of using inner_join() from the dplyr package to add the id column to the second data set.
DF <- data.frame(id = 1:3, label = c("AT", "BE", "BG"), x = c(6,5,7), y = c(0,8,9))
DF2 <- data.frame(label = c("BE", "BG", "AT"), x = c(6.8,5.8,7.8), y = c(0.8,8.8,9.8))
DF2
#> label x y
#> 1 BE 6.8 0.8
#> 2 BG 5.8 8.8
#> 3 AT 7.8 9.8
library(dplyr, warn.conflicts = FALSE)
DF2 <- inner_join(DF2, select(DF,id, label), by = "label")
DF2
#> label x y id
#> 1 BE 6.8 0.8 2
#> 2 BG 5.8 8.8 3
#> 3 AT 7.8 9.8 1
Created on 2020-11-27 by the reprex package (v0.2.1)