The .ASMDOT file type is for an Solidworks Assembly Template file.
Unless you are mixing your terminology, I don't know why someone would create a working Routing design and hand it off to you as a template format, unless you would be creating multiple interpretations or customizations upon a base assembly. I am unclear if you want to use this template, or if you should have received a .SLDASM file instead for a true assembly.
To use an .ASMDOT file, Open Solidworks and Open File, use the drop down located above the Open and Cancel buttons to select Template. Once you select template, your navigated location automatically changes to the File Location in System Options where you have it set for Document Templates (conveniently the first option in the list under System Options - File Locations). This can be either a local location or a shared network location, of the two I would prefer network location so that all users can use the same templates. If this is not the location where you had saved the file you want to open, then you can either move the file to that location or navigate to it manually to locate it. Then click Open once you have located and selected the file created for you.
Welcome to the forums. I hope we can be more helpful once your question is clear.
I recommend reviewing the dense collection of advice links found at: How do I do this SOLIDWORKS Forum thing? for things like tips on a good question, applicable references to include (SW year version including service pack), and attaching a file to a post.