Apart from the weapon, there are two things you must begin to improve swords, shields, axes, and so on. You'll need a type of Elden Ring Runes Smithing Stone and a smithing table, both are available quite early in the game.
The first smithing table found right at the beginning of the game at the Church of Elleh. To to the left of the merchant in this area is the table for smithing. If you play around with it, you'll see that you are able to "strengthen armament." From this point you'll be able upgrade shields and weapons until +3. This is the highest level this table can handle, so to upgrade past +3, you'll have to attend the blacksmith's shop, Smithing master hewg at the Roundtable Hold. From there, the procedure follows the same procedure as before use the appropriate size and type of Smithing Stones to upgrade your weapon to +10 or +25, depending on the weapon.
In order to upgrade it is possible to upgrade two weapon types: Normal and Special. The Normal guns require normal Smithing Stones, while the Special weapons require Somber Smithing Stones. A normal weapon may be upgraded up to +25, and Elden Ring Items for sale Special weapons are limited at +10. Be aware that Special Weapons are typically rewarded by beating bosses or revealing secrets.