lm is a base R function - meaning that it is available by default everytime you start R without having to load any libraries. You can just call it using lm(y ~ x, data = my_data) assuming that you have a dataset named my_data with variable y and x in your global environment.
If you are looking for something more specific than that, you will need to provide us with more information to be able to help you. Preferably in the form of a self-contained reprex (short for reproducible example)? It will help us help you if we can be sure we're all working with/looking at the same stuff.
install.packages("reprex")
If you've never heard of a reprex before, you might want to start by reading the tidyverse.org help page. The reprex dos and don'ts are also useful.
What to do if you run into clipboard problems
If you run into problems with access to your clipboard, you can specify an outfile for the reprex, and then copy and paste the contents into the forum.
reprex::reprex(input = "fruits_stringdist.R", outfile = "fruits_stringdist.md")
For pointers specific to the community site, check out the reprex FAQ, linked to below.