conbine two narrowPeak files into one for peakfile reading

[Renfang2019]

Dear Alicia, I run the single sample of bulk ATAC and now I would like to run two samples of bulk ATAC data. In your note, you recommend to combine two files. Can you please show me how to combine these two files? If you could give me the script, that would be wonderful. I am new to R so your help would be great appreciate! Thank you very much.