Hi 
Best to just get the official guides, even if it's just 1 chapter at a time as needed
http://wiki.documentfoundation.org/Documentation/Publications
You can get the full guides from there and there are also links to printed copies via Lulu "on demand" and also 3rd party documentation. The printed guides and some of the 3rd party documentation sometimes costs money but you can download the official guides for free.
The help files that you are
trying to install are well worth forgetting about. They are quite
helpful but are really quite out-of-date now. It's handy to have quick
help available from inside the program in quick bite-sized chunks but
much of it may be wrong or incurrate or even misleading now. The docs team could really use a hand because the program is developing faster than the small team of writers can write! They are quite prolific but most Office Suites only need a new set of guides once every 3 or 4 years. LO needs a new set every 6 months! So i would stick with the official guides and forget the in-built help if it's not easy to install.
Slackware!! Blimey! It's a tough one to pick for a first venture into Gnu&Linux-land! Most people tend to go with one of the noob-friendly point&click "gateway" distros such as Ubuntu, Mint, Mageia. However it does have quite a few advantages for a 1st venture.
Allegedly Slackers are dead-set against Office Suites. If you have not yet posted the question to LinuxQuestions.Org then consider (just for this question);
1. Posting in a more general forum and avoid the specifically slackware one
2. If you do post in the Slackware area then perhaps rephrase it in a more general way such as "How does one install something when there is no SlackBuilds script yet?"
If you have managed to get LibreOffice working then you deserve congrats. You are a far more advanced Gnu&Linux user than most of us that have been using Gnu&Linux for many years. (That's an accolade you quickly gain when using something as tough as Slackware and one of the advantages of using it)
Congrats and regards from
Tom 