Draw a picture and show whats going on - draw vectors for the current direction, magnetic field and the force. See Section 29.3 and Example 29.3 as well. Because its a proton you know mass and charge. Once you've found the force you can relate it to the centripetal force required for circular motion. Remember - and if energy is conserved you can relate change in potential energy to change in kinetic energy.
Angular frequency is given by Magnetic force on a straight current carrying wire .
The vector is the length of the straight wire segment and the direction of the positive current. For a curved wire, we must break the wire into short line segments. Torque - , where is the vector from the axis of rotation to where the force is applied. Torque on a current carrying loop , where is the magnetic dipole moment, which for a current carrying loop is , where is the area vector of the loop.