You need type all the text lines in the code block, when you enter EOF at the end the command will be executed.
This code block is creating a new file with the specific content, so if you will type it by hand in dom0 then you can type it directly in the file.
Create a directory:
sudo mkdir -p /etc/qubes/templates/libvirt/xen/by-name/
Create file:
sudo nano /etc/qubes/templates/libvirt/xen/by-name/YourQubeName.xml
Type this content in the file and save it:
<!-- import default template-->
{% extends 'libvirt/xen.xml' %}
<!-- we wanna alter the devices block -->
{% block devices %}
<!-- import default device block -->
{{ super() }}
<!-- manual video config -->
<video>
<model type='vga' vram='32768' heads='1' primary='yes'/>
</video>
{% endblock %}