It depends on how you will share your prototype–where you publish/post it and how people/devices will access it.
If you are publishing to Axure Cloud or another server and you know clients (browsers, computers, devices, etc.) have web access, then you will want to map your local font to a web font and set up the web font to be served in your prototype’s HTML. Since Averta is a licensed font you will likely need a web font license to get access to it’s @font-face and/or CSS. Or, you can search for free alternatives–basically, a site that hosts the CSS so the font can be downloaded and rendered. You might want to look into security risks with this, however. Another option is to convert your local font file to a custom web font and then upload that to your own server (see this thread for info: Help with Web Fonts)
Once you have access and rights to the web font, you should be able to find its @font-face or CSS code. Look for instructions on the host website for including or embedding the web font. Here is the Axure documentation for doing this:
If you have a situation where the device running your prototype does not have web access (e.g., mobile prototype or a usability lab without external internet access) you can embed the entire webfont code in the @font-face box of the web font options in the HTML code generator (refer to documentation above.) This will increase the size of your prototype.
Here is the template, where “MyFont” is the name of your font and “MyEncodedFont” is your converted webfont code (a really long string.) This assumes you are using a TrueType format, but other formats work as well.
font-family: MyFont;
src:
url(data:font/ttf;base64,MyEncodedFont) format("truetype");