You can't. level 20 is as high as it goes. Well it was until Fire Emblem: Radiant Dawn. Transforming human/beasts known as Laguz can go to level 40. You CAN however use a Master Seal, Knight's Crest, etc. to evolve a character above level 10 to a new, more powerful class.
I found a guide on the net, the link is posted below.
The last Fire Emblem to come out was Fire Emblem: Shadow Dragon for (DS). Past US titles include... Fire Emblem (GBA), Fire Emblem: The Sacred Stones (GBA), Fire Emblem: Path of Radiance (GameCube) and now Fire Emblem: Shadow Dragon (DS). Fire Emblem: Path of Radiance is the prequel to Fire Emblem: Radiant Dawn and Fire Emblem (GBA) is the prequel to Fire Emblem: Shadow Dragon (DS). There are more Fire Emblem games in Japan, but no others have been translated.
1. Fire Emblem: Ankoku Ryuu to Hikari no Tsurugi 2. Fire Emblem Gaiden 3. Fire Emblem: Monshou no Nazo 4. Fire Emblem: Seisen no Keifu 5. Fire Emblem: Thracia 776 6. Fire Emblem: Fuuin no Tsurugi 7. Fire Emblem: Blazing Sword 8. Fire Emblem: The Sacred Stones 9. Fire Emblem: Path of Radiance 10. Fire Emblem: Radiant Dawn 11. Fire Emblem: Shadow Dragon 12. Fire Emblem: Shin Monshou no Nazo ~Hikari to Kage no Eiyuu~ 13. Fire Emblem Awakening
No, Fire Emblem Sealed Sword is Fire Emblem 6. Fire Emblem 7 is the prequel to Sealed Sword and are separate games.
In just about every level, someone comes or leaves.
Marth and Ike are both in the Fire Emblem series, but are not in the same game. Marth is in: Fire Emblem: Ankoku Ryuu to Hikari no Tsurugi Fire Emblem: Monshou no Nazo Fire Emblem: Shadow Dragon Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu while Ike is only in: Fire Emblem: Path of Radiance Fire Emblem: Radiant Dawn Both are also in Fire Emblem Awakening but as add on content
Marth is in: Fire Emblem: Ankoku Ryuu to Hikari no Tsurugi Fire Emblem: Monshou no Nazo Fire Emblem: Shadow Dragon Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu He is also 'in' Fire Emblem Awakening, but only is available as add on content
The GameBoy Advanced as the most Fire Emblem games. Fire Emblem: Fuuin no Tsurugi, Fire Emblem: Blazing Sword, and Fire Emblem Sacred Stones were all released for the Nintendo GameBoy Advanced.
You level up your characters and go through the levels
Fire Emblem is not in Pokemon Emerald.
The final boss in Fire Emblem 7 is the Fire Dragon.
Marth and Roy are both from the Fire Emblem series but are in different games. Marth is in: Fire Emblem: Ankoku Ryuu to Hikari no Tsurugi Fire Emblem: Monshou no Nazo Fire Emblem: Shadow Dragon Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu while Roy is only in Fire Emblem: Fuuin no Tsurugi. He is seen in the secret ending of Fire Emblem: Blazing Sword as well. Also, both characters are in Fire Emblem Awakening, but only are available as add on content