[R] Need help plotting

[DFP]

I'm trying to do as you suggest, but I'm not understanding what I need 
to do.  I asked what the line pivot_longer(-time, names_to = "y1") would 
do if applied to this df:

 > tst
     time y1 y2
1  18:55 30 19
2  18:56 30 19
3  18:57 29 19
4  18:58 31 19
5  18:59 28 19
6  19:00 28 19
7  19:01 28 19
8  19:02 28 19
9  19:03 28 19
10 19:04 28 19
11 19:05 29 19

I tried to run these lines and then look at tst, but this is what I get:

 > tst %>%
+    mutate(time = paste(Sys.Date(), time),
+                  time = as.POSIXct(time)) %>%
+    select(time, y1,y2) %>%
+    # reshape to long format
+    pivot_longer(-time, names_to = "y1")
Error in tst %>% mutate(time = paste(Sys.Date(), time), time = 
as.POSIXct(time)) %>%  :
   could not find function "%>%"

How can I learn what the pivot_longer has done to tst?

Darn it--Now I try to run the whole sequence that Rui suggested--it 
worked before--and now I get this:

 > tst %>%
+    mutate(time = paste(Sys.Date(), time),
+                  time = as.POSIXct(time)) %>%
+    select(time, y1,y2) %>%
+    # reshape to long format
+    pivot_longer(-time, names_to = "y1") %>%
+    # now plot
+    ggplot(aes(time, value, color = y1)) +
+    geom_line() +
+    geom_point() +
+    scale_color_manual(values = c("orange", "skyblue")) +
+    # make datetime labels
+    scale_x_datetime(date_breaks = "1 mins", date_labels = "%H:%M") +
+    theme_bw()
Error in tst %>% mutate(time = paste(Sys.Date(), time), time = 
as.POSIXct(time)) %>%  :
   could not find function "%>%"
 >

What should I try next?