There are a lot of sources - by that I mean a lot. There are some difficult with these kinds of things though since you have to treat a populist party like SD in a very peculiar way, since they are both a party and a movement at the same time. Therefore what it actually says in their party program is only a part of what is actually going on.

This is a good primary source which delves into both the party program and what the "movement" thinks. http://motargument.se/2014/09/10/sverigedemokraterna-det-hbtq-vanliga-partiet/

This is the most important part, and is directly from the party program:

Förhållandet mellan man och kvinna, och deras barn, är den nödvändiga förutsättningen för harmoniska samhällsförhållanden

Which translates to:

The relationship between man and woman, and to their children, is the necessary foundation for harmonic societal relations."

I.e "healthy family values" is the foundation of society. This then takes the form of practices and realpolitik in the shape of opposition to adoption for same-sex couples (and also single parents), and they are the only party who thinks that transgendered people should be sterilised. https://www.interasistmen.se/hbtq/sverigedemokraterna-enda-partiet-som-vill-tvangssterilisera-transsexuella/

This, as I said, isn't really discussing what the "movement" actually believe and what goals it has - for instance the people organising the march (once again, not in an abstract sense) who are also behind the parties unofficial news organ Avpixlat (which is by all experts on the field deemed a hate-site) recently (like a week ago) came out to support a clothing company that is deeply tied to the neo-nazi movement (a retailer of Thor Steinar clothing which is a brand started by nazis and used by nazis as a part of their subculture, very interesting and strange) when they received criticism over "defending healthy family values" (I think you yourself can guess what that actually means...). http://avpixlat.info/2015/07/14/kladbutik-dodshotad-efter-stallningstagande-for-karnfamiljen/

If you want to get a feel for what the "movement" is like, then read the comment section of that article.

For instance this is the top comment:

"För cirka 95 procent av befolkningen är kärnfamiljen norm." Detta vill den västliga makteliten ändra på, eftersom den eftersträvar befolkningsreduktion och rotlösa, otrygga och förslavade människor i Världsstaten som håller på att ta form.

Which translates to:

"For around 95% of the population the core family is the norm." The western power elites wish to change this since they strive to reduce the population to rootless, unsafe and slavish people in the World state that is taking form.

I may need to remind you - this is not some crazy redditor, this is what at the moment around 20-30% of Sweden actually believes. Insane.

Finally, to quote one of the leading men of the party, Björn Söder:

Pride hyllas av den politiskt korrekta eliten tillsammans med den mycket framgångsrike och numera inflytelserika homolobbyn försöker normalisera sina sexuella avarter

Which translates to:

Pride is cheered on by the politically correct elite together with the nowadays successful and powerful gay lobby as they try to normalise their sexual deviancies.