There are multiple ways to get new players.
You can get new players by opening Packs. Packs come with varying players of different rarities/qualities. Some packs contain only 1 player, some 4 or 5, up to even 20. You can get packs by buying them with Coins or Gold Bars, unlocking them as rewards or completing Missions or Player Trade Challenges.
You can also get new players through the dynamic Transfer Market. Here you can buy and sell players to/from other FHC users.