To take tips from an appointment schedule page, locate the unpaid appt, click it, then click pay. You'll see an option to add a tip.
To use the tip feature in POS, add the item first (class, appt, etc), then click Add tip.
You'll also find tips listed in your payroll reports. The Combined Payroll Report has its own tips section down at the bottom. To see this, click Analytics > Reports > search Payroll.