Combine full month name (Eg. January, February etc) and Year (Eg. 2018,2019 etc) from two columns into date

This is my first question on Stackoverflow. I have recently started to use R programming. I have a dataset where month and year are in two columns.

Year     Month 
2019     January
2018     February
2019     April
2018     June

This is how my data look like. I want to combine these two columns and use it as a time series in R.