To create a sketch:
Mockup covers numerous and various templates to assist you in putting together your projects. It provides 45+ diverse options for iPhone, iPad, Apple Watch, Web, Mac, TV, Android, Widgets, App Icon, and Blank templates. Each has its size and characteristics. Some have landscape & portrait orientations.
The sketch starts with a single frame. To add up frames horizontally, swipe to the left. An arrow (→) will appear. Swiping will be held until a (+) appears.
Once the (+) pops up, release your finger. A new column adjoins the previous one.
Similarly, swipe upward to add a new row.