Then go to:
The your “yourdomain.tld” folder and then once you enter you can see an htdocs folder and enter that htdocs folder and there you can upload and modify your file.
This really only requires common sense and understanding if you ask me.
I understand you, I am using the Translator, since I speak Spanish. I will tell you again but I will do it directly in English:
EN: I have the domain example.RF.GD that generally we have at start in Infinity. I want to change this domain for new domain and when i use the new domain the page show the content, themes, etc… normally.
ES: Tengo el dominio RF.GD que la pagina Infinity nos d generalmente, quiero cambiar este dominio RF:GD por un dominio propio y que cuando yo entre a este nuevo dominio la pagina muestre el contenido, plantillas, temas, etc… normalmente.
If you still do not understand, tell me to know how else I can explain. Thank you.