How do I add cardio to my lifting? (Or vice versa?)

For those that want to do both, with strength and size gains being your primary goal, check out Special Endurance Sport Considerations for Strength Athletes and Endurance Training for Strength Athletes Part 1 & Part 2. Greg Nuckols also gives recommendations in his Stronger by Science articles Practical Considerations for Combining Cardio and Lifting and Avoiding Cardio Could Be Holding You Back.

Conversely, if you want to do both but improving endurance in your primary goal, check out A Guide to Strength Training for Endurance Athletes Part 1 & Part 2