Can できます

There are a couple of ways to say "I can..." in Japanese.  The easiest is できます dekimasu.  Let's look at how to form some sentences. 

CAN + NOUN [できます]

1

日本語 が できます。 nihongo ga dekimasu.
I can (speak) Japanese. [I can do Japanese.]

2

漢字 が できます。 kanji ga dekimasu.
I can (read/write) kanji. [I can do kanji.]

3

スカイダイビング が できます。 sukaidaibingu ga dekimasu.
I can skydive.

CAN + VERB [こと が できます]

Actually, the above are all shortened versions without the verb.  Let's add the verb.  koto means thing, but here it is used to make a verb a noun so it will work with dekimasu.

1