In the assemble options, define the path to your assets directory:
options: {
assets: 'dist/assets'
}
Now, in your templates you can use the variable like this:
{{assets}}
For example:
<link href="{{assets}}/theme.css" rel="stylesheet" type="text/css">
Renders to:
<link href="dist/assets/theme.css" rel="stylesheet" type="text/css">