There's a quick section on exactly this in R for Data Science here:
You might have to dummy up minutes (I assume you can just use 00). I'm excerpting R4DS here, but the link will take you right to the section. You'll need to load the appropriate libraries (library(tidyverse) and library(lubridate) should cover it, I think).
Instead of a single string, sometimes you’ll have the individual components of the date-time spread across multiple columns. This is what we have in the flights data: