[ubuntu] How does one create a script and run it? topic

If I could turn the following commands into a script that I can point at a directory of photos and run it would simplify my life a lot. The problem is I have no idea how writing a script is done and I could use some help. Thanks in advance

Code:

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find . -name '*.NEF' | gawk 'BEGIN{ a=1 }{ printf "mv \"%s\" SubjectName_%04d.NEF\n", , a++ }' | bash
mkdir jpgs
mogrify -path Fullpath2/jpgs -format jpg *.NEF
cd Fullpath2/jpgs
mogrify -resize 2048x2048 *.jpg
mogrify *.jpg -gravity center -draw "image over 0,0 0,0 'Fullpath2/Watermark.tif'" *.jpg

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(obviously SubjectName and Fullpath2 need to be replaced as needed.)