First, you will just need to click the + New Job button at the top left of the screen:
From there, you will be taken to the job creation page:
You can then search for or create the overall client the job is for, select or create a site details (i.e. the location of the job itself and who you will be dealing with onsite), choose the job type and enter a quick title and description like so:
Once done, you can then click the the create job button to finalise it, and be taken to your new job card.
For more info please: