Wisdom is the druid’s spellcasting ability. The details are located on p. 66, Paragraph 6 of the PHB (Player’s Handbook) under the Spellcasting header.
Your DC will be 8 + your proficiency bonus (which is +2 for a level one character) + your Wisdom modifier. Let’s say you have a Wisdom score of 14; that means your modifier is +2. That puts your total spell save DC at 12 (8+2+2).
Your spell attack modifier is equal to your Wisdom modifier + your proficiency bonus, which equals +4 in this case.
This means that if you cast a spell that requires a spell attack roll, you will roll a d20 and add 4 to it.
Here is a link to a video about casting spells in Dungeons & Dragons that you might find useful.
If you don’t have the PHB, here is a link to the basic rules; you should find everything you need under the druid tab in classes.