Although the Alexa/Echo Dot help pages suggest that you need to use a specific App on a tablet or smart phone, you can set up the Echo Dot with any Windows PC that has WiFi. I suspect the same is true for Mac PCs as well.
When in set-up mode, the Dot puts out its own WiFi signal that the configuring device has to connect to. This is an open WiFi connection so there is no pass phrase at this stage. The Dot will list all the WiFi networks it can see. Choose your home WiFi network, then if requested, enter the pass phrase for your home network, which you should be able to get by logging in (not just connecting to) your router if you do not know it. If your home router has not had the pass phrase changed then it can be written on the router's label or be in the manual or set-up guide.
Once the Dot is connected to your home WiFi, it will turn off its own WiFi signal at which point you should switch your configuring device back on to your own network.
You will also need an Amazon account that the Dot will connect to. If you already have an account you can use that, or set up a new account just for the Dot. For example, if you have one-click ordering on an Amazon account, you might not want this facility to be available through the Dot.
I hope this helps.