Can you tell me how specifically the second KKK contributed to the Johnson Reed Act of 1924? I know that they instilled fear in the general public of immigrants, etc. But what specifically did they do in order to get Congress to pass that law? Did they have members in Congress? I read that that law is a victory for them but I can't find information on specifics. Thanks

Firstly, it is important to remember that since its inception during Reconstruction, the Ku Klux Klan has been a secret organization. This is part of the reason why they wore hoods to shield their faces. It is very likely that there were members of Congress who were members of the Ku Klux Klan. It is also possible that members of Congress have been members of the Klan rather recently, and such an affiliation would influence policy. However, because we do not know which members of Congress were in the Klan, we cannot know which members supported the act for this reason.
Congress passed its first restrictive immigration law in 1917, capitalizing on concerns over national security and lingering desires for isolationism after the First World War. The 1917 law instituted a literacy test, increased the entry tax, and allowed immigration officials more discretion in determining who could enter the United States and who could not. It also established the precedent of keeping out Asians who did not come from Japan or the Philippines. The latter country was a U.S. colony, so its citizens could come and go as they pleased. The Japanese government had entered a "gentleman's agreement" with the United States ten years before, agreeing to limit the number of its immigrants to the U.S.
However, by the 1920s, officials realized that the literacy test would not be enough to exclude "undesirables." William P. Dillingham, a Republican senator from Vermont, introduced immigration quotas, "which he set at three percent of the total population of the foreign-born of each nationality in the United States as recorded in the 1910 census." That only allowed for 350,000 new immigrants to get entry visas each year. The new calculations allowed for many new immigrants of British descent, and many others still from Western Europe, but fewer from Eastern and Southern Europe. Furthermore, Asians not previously excluded from immigrating, including the Japanese, were now barred. Many in Japan were offended, as the United States had clearly backed out of its previous agreement. The law and the United States's clear interest in maintaining a white, Western European racial composition contributed to increased tension between the nations.
For the Klan, this was ideal. The organization had revived itself in 1915, but gained strength after the First World War. Within a year of its revival, it had 100,000 new members, all united against black people, the Japanese and other "Orientals," Catholics, Jews, and other foreign-born individuals.
Senator Dillingham was a proponent of Progressive Era beliefs, including Social Darwinism, which encouraged the exclusion of groups considered detrimental to American society and culture. He had this wish in common with the KKK, which had explicitly defined American culture as "white," "Anglo-Saxon," and "Protestant."
In sum, the passage of the Johnson-Reed Act was probably less about explicitly racist lobbying from the KKK and more about an agglomeration of forces coming together at just the right time: isolationist sentiments revived among the public, lingering Progressive Era ideas about social preservation and social engineering, and nativist ideas from the Ku Klux Klan. I do not agree with the notion that the Klan "instilled" fear in the public regarding foreign influence. Instead, that fear had already existed and was merely stoked by the organization. The Johnson-Reed Act was "a victory" in that it was aligned with the Klan's nativist agenda.
https://history.state.gov/milestones/1921-1936/immigration-act