How should てあがる be used？


Ive seen 立ち上がる＆乗ってあがる before,yet I can't tell the difference between them and
立つ｜乗る。

For example 早速立ち上がれ！（Hurry and stand up!)

エレベーターに乗ってあがる (=I take the elevator and go up.).

I haven`t seen any other usage for てあがる。




First, let's make a clear distinction between `te-form + 上がる` and `masu-stem +
上がる`. The former is just two verbs combined using the te-form. 乗って上がる is not a
set phrase but just consecutive two actions, エレベーターに乗る and 上がる.

The latter form is called compound verbs. Just as in English you can join a
verb and an adverb to describe a distinct action (e.g,. "carry out", "take
off"), in Japanese you can join two verbs and mean something different. The
Japanese language has tons of compound verbs, and there's even [a dedicated
database site for compound verbs](http://vvlexicon.ninjal.ac.jp/en/). 上がる
after the masu-stem is roughly similar to "`verb` + up" in English. 立つ means
"to stand" whereas 立ち上がる means "to stand up". 燃える is "to burn" and 燃え上がる is
"to flame up". `masu-stem + 上がる` also often means "finish ～ing". Some verb
pairs are unpredictable; for example
[盛り上がる](http://jisho.org/word/%E7%9B%9B%E3%82%8A%E4%B8%8A%E3%81%8C%E3%82%8B)
meaning "to get excited." Use the "Search by V2" function of the lexicon above
to find lots of examples. There is no such word as 乗り上がる in Japanese, but
there is
[乗り上げる](http://jisho.org/word/%E4%B9%97%E3%82%8A%E4%B8%8A%E3%81%92%E3%82%8B).

