There are five primary ways to add assets to a Kit in Lingo.
Files To insert files using the Insert Panel simply drag the file icon from the Insert Panel and drop it at the precise location where you want the files to display in the gallery.
Colors To insert a color swatch simply drag the color icon from the Insert Panel and drop it at the precise location where you want the swatch to display in the gallery. You can read more about inserting colors in this article.
Drag n Drop
You can drag any accepted file type and drop it into Lingo. To do so simply grab the files you want to add to Lingo and drop them into either the Gallery or into a Section in the Navigator. If you drop them into the Gallery you can choose the precise location where the new assets will be added.
If you drop them into a Section in the Navigator the new assets will be appended to the bottom of that Section.
Copy n Paste
You can copy any accepted file type and paste it into Lingo. To do so simply copy the files you want to add to Lingo and paste them into a Kit. If you don't have any assets in the Kit selected the pasted assets will be appended to the bottom of the Section in focus. If you do have an asset in the Kit selected the pasted assets will be inserted after the selected asset.
If there are existing assets in a Kit you can add additional assets by selecting an asset and right clicking it > Insert. The new assets will then be inserted before the selected asset.
Sketch components can ONLY be added to Lingo via the Sketch Plugin.