To host a giveaway you need to use the Link-Up tool.

You can set up the duration the giveaway is taking place as well as a number of other options. 

Once you set up your giveaway through the Link-Up dashboard you can copy the generated code and paste it on your blog.

All the participants can then click a button to enter their name and email (not publicly available) right inside your post. 

You can ask for a URL if the giveaway is based on a contest and they must submit a photo of their project among other options.

Moderation is available and you have full control of the entries. Each entry has a number. 

Once the giveaway is closed, choose a number randomly or based on the entries of your contest. 

You can find all the info (email, URL, name) of the entries in the link-up dashboard.