Visit the official Tomb Raider website or forums to see if the developers have made any language packs available for download. You can also check the game's support page for any patches or updates that might include the English voice pack.
If you're playing on a PC, check the game client or launcher for any available language packs. Some game launchers, like Steam or GOG Galaxy, offer language packs as separate downloads. Tomb Raider 2013 English Voice Pack Download
The size of the English voice pack may vary depending on the source and method of download. Be prepared for a potentially large download size ( several hundred MB). Visit the official Tomb Raider website or forums