"I did a lot of work and got tired."
して is the continuative base form of する (do). The continuative base form basically means it's used to move the sentence forward into making another point。
I see. I kind of get the usage of して here now. I am a bit confused because I always thought しごと is a noun while はたらき is the verb.
Same here, I am really thrown off by this currently. I suppose shigoto shimasu is quite literally "to do" + "a job".