時代 means ”era” and the を particle indicates that 時代 is the direct object of the action 創る meaning “to create”.
For learners who are learning kanji, there are three kanjis for つくる.
- 創る – “to bring something new and original into existence” such as new school, new world and so on. Kenshin is talking about creating the new era so this kanji is used.
- 作る (more commonly used) – “to form something small or something intangible by putting things together” such as food, songs, and so on.
- 造る – “to form something tangible on a large scale by putting things together” such as ships, money and so on.
The の particle makes the verb work as a noun. So 時代を創るの means “the ones who create an era”.
The grammar is AではなくB meaning “not A but B”.
The A is 刀 meaning “a Japanese sword” and the B is “それを扱う人”.
それ means “it” which is 刀, を is the direct object particle, 扱う means “handle or wield something” and the clause それを扱う modifies 人 meaning “people”, so それを扱う人 means “the people who wield the swords”. Therefore, 刀ではなくそれを扱う人 means “not swords but the people who wield the swords”.
Lastly, でござる – I’m sure you’ve never heard this in real life but it’s often used by ninja or samurai in anime. It was actually used by samurai like Kenshin in the Edo era. So if I change this sentence into the modern style, it will be 時代を創るのは刀ではなくそれを扱う人です. Also, ではなく sounds stiff and formal so じゃなくて is often used in casual speech.