There is no simple way, if any.
As opposed to the faux italic that some software can create, Adobe requires you to install an actual font file. This is because, for a lot of typefaces, the italic is very, very different in shape from the roman variant. This is especially true for classic serif types, in which some letter shapes change structure between roman and italic. Don't be mistaken: creating an italic is not just slanting the letterforms.
The same goes for bold in a lesser degree. Bolds aren't just made by making the letter shapes thicker. Look closely at the roman and the bold for any professional typeface and you'll see that shapes are fundamentally different, in a way that you can't recreate with a piece of software.
Yes, browsers and programs like office and their ilk allow you to italicise or boldify any font. They slant, thicken or otherwise edit the letterforms in some standard way. It may serve its purpose, but it's not the 'true' italic or bold.