First, please review the protocol for asking questions. You got downgraded because you (1) did not provide a reproducible data set and (2) asked a question answered elsewhere here.
Here is a quick answer though:
library(twitteR);library(dplyr); library(ROAuth)
#set API Keys; to obtain, go here: https://apps.twitter.com/ and make an application for your twitter account
api_key <- "paste yours here" # create a set of 'keys' & 'tokens'
api_secret <- "paste yours here"
access_token <- "paste yours here"
access_token_secret <- "paste yours here"
setup_twitter_oauth(api_key, api_secret, access_token, access_token_secret)
#grab latest tweet data
tweets1 <- searchTwitter('@oprah', n=1000)
TweetsBy1<-twListToDF(tweets1) #convert to dataframe
TweetsBy1$account<-"Oprah" # useful to have this
glimpse(TweetsBy1) # look at your data; the text variable is what you're after
temp<- TweetsBy1 %>%
group_by(created) %>% # you will need to reformat this date variable
summarise(numTweets=n())
TweetsBy1$text # this is the text of the tweets
ggplot(temp, aes(created,numTweets))+geom_bar(stat="identity")+
theme_bw()+ylab("Number of Tweets")+
ggtitle("Number of Tweets by Date")
As for text analysis, that's a whole other ball of wax. See the tidytext
package for more info.