You need to find the aircraft and install them in the sim. The F-15E, for instance is here:
https://militaryaiworks.com/download-ha ... -f-15e-fsx This file only includes a few Lakenheath paints, but it will get you started. Download and extract the folder, which will include a 'readme' file and a Manual .pdf both of which include installation instructions.
The post above yours includes two traffic files. One of them is for the F-15Es of the 48th TFW at Lakenheath, and this needs to be installed in \scenery\world\scenery. The 48th Wing file has already been coded for the JYAI F-15E in the first paragraph.
Once you've completed this exercise you will have a basic understanding of how to install 3rd-party traffic into FSX:SE. It's actually very easy! You can then search for and install the other types at EGUL (F-35, HH-60) in your own time. The Download Hangar here includes enormous numbers of aircraft, bases and repaints; sufficient to equip most of the world's military air arms, and covering several periods.