I really recon you to have a look at aldeed’s tabular package, which does all the work for you and works really well. Here you go - have fun with it https://github.com/aldeed/meteor-tabular
Also note, that the package-based structure is NOT recommended anymore… it was something we liked to do in the good old days of meteor. The way to do it today are ES2015 modules… check out this link here, where it is explained very well https://guide.meteor.com/structure.html.
The way to manually include datatables today (I still recon you to use aldeed:tabular) would be to do an meteor npm install datatables-package (https://datatables.net/download/npm) and then in your onRendered() you should be able to attach it to the dom