Where are you coming from? North of the parks or south? If coming from north of the parks, park in the Mickey & Friends parking structure. The flyover is the ramp from the 5 fwy (southbound) the exits for
Disneyland and takes you directly to M&F. Be aware that the flyover isn't always open -- so don't get caught off guard. Just watch the overhead signs. (If the flyover isn't open, you'll just use the regular freeway exit.) If you are coming to DLR from the south, park in the Toy Story lot on Harbor. Both lots cost $25/day for all day parking with in and out privileges (keep your parking stub to show the CMs).
Getting to the parks: M&F has a tram to the parks from the structure. You'll go through bag check/security before getting on the trams. The trams drop you off in DTD. From there, it's a very short walk to the esplanade between the parks -- maybe 2 minutes? Left for DL, right for DCA.
Toy Story has shuttle buses that take you to the Harbor side entrance for the esplanade between the parks. You'll go through bag check/security before entering the esplanade. Once you go through bag check, you'll enter the esplanade and choose which park you want: left for DCA, right for DL -- easy!
If your hotel is walking distance to the parks, don't drive -- save the money and time involved. Just walk. If your hotel is close, but not walkable -- you might think about using Uber/Lyft. A roundtrip ride might be less than $25/day. Just something to think about. Driving and parking at DLR adds a lot of time and money on to your trip, so it's worth thinking this through.