Trying to install an .sh file but this error keeps returning:

I've also tried using things like ./install_seq.sh and similar.
Also, when simply typing install_seq.sh there's another error:

Someone suggested dos2unix but I can't get it to download on my computer and I don't know if there's another solution?
Trying to install an .sh file but this error keeps returning:

I've also tried using things like
./install_seq.shand similar.Also, when simply typing
install_seq.shthere's another error:Someone suggested dos2unix but I can't get it to download on my computer and I don't know if there's another solution?