Circular polarized micro-strip patch antenna
The width of the microstrip feed will be calculated using the effective permitivity of your PCB substrate material, search for transmission line impedance calculators. You will need all the physical parameters of the substrate you are using. Typical system impedance is 50 Ohms.
The position is likely at the center of the edge of the patch, but I'd look for references in Pozar's Antenna Theory book or in the literature for exact design dimensions. You can also iterate the feed positions in your simulation to find the place that gives the best axial ratio for your operating frequency.
The exact position is irrelevant so long as the phase phase length difference between the two transmission line sections is 90°. You should likely instead use a quadrature hybrid (search this) since the 90° phase difference between ports will be maintained over a wider bandwidth, although patch antennas are inherently narrowband anyway unless parasitically loaded (look up stacked patches).