why do you need to have seen him before?
For example, you could see a panel that shows a large screen showing all the statistics going on in the invasion. A figure would be sillouhetted against it.
Next panel shows a technician monitoring the screen, who then turns towards the figure, and explains the invasion has failed. Another still panel with no dialogue.
Next panel is basically the same, but has the figure comtemplating to himself about how he will get his revenge or something like that, and the next panel shows his face, ending with his vow to destroy Captain America and all that he stands for.
If the visual hint is strong enough, most people would realize that this individual is Red Skull, and set him up for a future appearance.