For starters, the rvest package site has some nice tutorials to help you get started. For example, the SelectorGadget article has nice tips on how to pull from a page the content you'd like.
You're also going to want to get into pagination with rvest. Thankfully your website has a pretty easy page scheme (https://www.vadibilisim.com/cantalar/{page_number}), so you can just run a loop to go through all the pages.
That tutorial has tips like how to pull text with html_text.
library('rvest')
url <- 'https://www.vadibilisim.com/cantalar'
webpage <- read_html(url)
# get product names on page
product_names <- html_nodes(webpage,'.urunBaslik') %>%
html_text()
product_names
#> [1] "Addison ADS-230 Siyah Kab..." "Addison 300448 15.6 Laciv..."
#> [3] "Addison 300448 15.6 Pembe..." "Addison 300448 15.6 Gri N..."
#> [5] "Valja VL-241 Noktalı Bey..." "Addison 300458 18 Siyah G..."
#> [7] "Addison 300682 15.6 Laciv..." "Addison 301008 15.6 Siyah..."
#> [9] "Addison 301004 15.6 Kamuf..." "Addison 301003 15.6 Koyu ..."
#> [11] "Addison 301005 15.6 Laciv..." "Addison 300492 15.6-16 Si..."
#> [13] "Addison ADS-202 Gümüş ..." "Addison 300998 15.6 Gri/S..."
#> [15] "Addison 301000 14 Gri/Siy..." "Addison 300997 15.6 Gri/S..."
#> [17] "Addison 300993 15.6 Koyu ..." "Addison ST-490 Siyah/Gri ..."
#> [19] "Addison 300494 15.6 Bordo..." "Addison 300441 15.6 Kamuf..."
#get product links on page
html_nodes(webpage,'.urunBaslik') %>%
html_nodes('a') %>%
html_attr('href')
#> [1] "/addison-ads-230-siyah-kabin-boy-valiz"
#> [2] "/addison-300448-15-6-lacivert-notebook-sirt-cantasi"
#> [3] "/addison-300448-15-6-pembe-notebook-sirt-cantasi"
#> [4] "/addison-300448-15-6-gri-notebook-sirt-cantasi"
#> [5] "/valja-vl-241-noktali-beyaz-prestige-serisi-pvc-orta-boy-valiz"
#> [6] "/addison-300458-18-siyah-gaming-bilgisayar-notebook-cantasi"
#> [7] "/addison-300682-15-6-lacivert-bilgisayar-notebook-cantasi"
#> [8] "/addison-301008-15-6-siyah-notebook-sirt-cantasi"
#> [9] "/addison-301004-15-6-kamuflaj-notebook-sirt-cantasi"
#> [10] "/addison-301003-15-6-koyu-gri-bilgisayar-notebook-cantasi"
#> [11] "/addison-301005-15-6-lacivert-notebook-sirt-cantasi"
#> [12] "/addison-300492-15-6-16-siyah-bilgisayar-notebook-sirt-cantasi"
#> [13] "/addison-ads-202-gumus-kabin-boy-pilot-valiz"
#> [14] "/addison-300998-15-6-gri-siyah-bilgisayar-notebook-cantasi"
#> [15] "/addison-301000-14-gri-siyah-notebook-sirt-cantasi"
#> [16] "/addison-300997-15-6-gri-siyah-notebook-sirt-cantasi"
#> [17] "/addison-300993-15-6-koyu-gri-bilgisayar-notebook-sirt-cantasi"
#> [18] "/addison-st-490-siyah-gri-gizli-fermuarli-bilgisayar-notebook-sirt-cantasi"
#> [19] "/addison-300494-15-6-bordo-sirt-cantasi"
#> [20] "/addison-300441-15-6-kamuflaj-desenli-sport-bilgisayar-notebook-sirt-cantasi"
Created on 2021-03-03 by the reprex package (v1.0.0)
It'd be helpful to be explicit about what you are trying to collect and the trouble you're having.